Fix NPE when stopping KeyAgreementTask, improve thread safety

This branch fixes #696 and improves the thread safety of the camera code, mostly by adding @UiThread annotations and occasionally by moving stuff onto the UI thread that might have happened on other threads before.

Closes #696

See merge request !345

Use new group metadata for showing lists

What was supposed to be a minimal change turned into a rather large MR. I did my best to keep things in separate commits, so I can still split this into smaller MRs if desired.

While making use of the new group metadata in the contact and forum list, I noticed some other things in need of improvement to get rid of needing to load all messages:
* Refactor `SharingManager` so its events provide message headers that can be used to update list items
* Add `GroupId` to conversation items, so the metadata of the respective group can be updated as well when marking the items read
* Create a very basic `ConversationManager` so the GroupCount for the various clients can be queried in one go without needing to know all their groups per contact
* Fix a nasty bug that caused forum and blog invitation to not update their read state
* Fix some bugs related to displaying the forum list with proper unread count

Some casual measurements with just a few contacts and messages showed a reduction of the contact list load time by one third.

See merge request !343

Fixes #531, #532

Fixes #373

Fixes #350

This is also lays the groundwork for #384

Refactor existing adapters into a generic superclass

This MR also moves various blog classes into their own packages and makes the required visibility changes.

Closes #687

See merge request !346

This commit also moves various blog classes into their own packages and
makes the required visibility changes.

Make body cache thread-safe, reduce visibility of classes

Closes #611

See merge request !347

Fix IntroductionManager unit tests

I forgot to run the unit tests after changing the `GroupCount` serialization in response to a review comment. This MR fixes the tests.

See merge request !344

Remove unused UI code and layouts

If we ever need this code, it will be in the git history.

Closes #598

See merge request !342

Merge branch '584-store-latest-timestamp-and-unread-count-in-group-metadata-for-private-messaging' into 'master'

Store message count, unread count and timestamp of latest message in group metadata

This is to eventually address #373 and slowness of other lists. The group metadata is not yet used, but if this MR isn't merged fast, another commit that actually uses it and thus takes care of the slowness will be added.

Closes #584, #585, #586

See merge request !336

in group metadata to be able to speed up group listings.

Closes #584, #586, #585

Release camera surface to work around Android bug #54285

Closes #680

See merge request !340

Clean up identicon code, remove unused classes

I noticed some debug-level logging coming from the identicon code, went in there to remove it, and realised half the code was unused, so I removed that too.

No functional changes except that the logging is gone and the opacity is now OPAQUE rather than UNKNOWN, which wasn't valid in this context.

See merge request !339

Remove loading callbacks from fragment listener

Now fragments are responsible for their own Progress bars.

Closes #642

See merge request !316

Emoji Support for all user input

All text that can be generated by users will show emoji from the shipped sprites by using the `EmojiTextView` instead of the normal `TextView`.

For all messages and posts, the custom emoji keyboard is now available as well. For this, a new `LargeTextInputView` has been introduced that is a sub-class of `TextInputView`. In order for the emoticon keyboard to work properly the existing views had to be modified heavily, sometimes resulting in new behavior such as scroll views now being above the fixed input field. Actual testing on a device (preferably with a tiny screen) is recommended to make sure this still works as expected. Screenshots will be included at the end of this post.

This MR also disables menu actions rather than hiding them and it includes a fix for a regression that was not showing the keyboard automatically in forums.

![device-2016-09-28-104914](/uploads/8ce9c8f61b32dc5a46b89a3a2cf1e6a4/device-2016-09-28-104914.png)
![device-2016-09-28-105026](/uploads/96ef9c40547c7a44fbc4517c87637a7e/device-2016-09-28-105026.png)
![device-2016-09-28-105041](/uploads/a0d1ed23ccb66e8bf9541737407142e3/device-2016-09-28-105041.png)
![device-2016-09-28-105440](/uploads/fb76ed2adc87600cfb0fc33c3962d4a6/device-2016-09-28-105440.png)
![device-2016-09-28-105515](/uploads/51f845d697cee3df38d1b9eef3c0ddfc/device-2016-09-28-105515.png)

Closes #92

See merge request !329

Fix regression in IntroduceeManager

This was happening when the remote response arrives before the local
response is made and thus the local response needs to be send with the
ACK following. The problem was that we ACK was sent before the response
which is not allowed and resulted in the session being aborted by the
introducee. This was happening, because recursion is hard ;)

The fix is only restarting another protocol engine to send the ACK
after the first run has been completed.

An integration test was added to prevent such regression in the future
and to test this code path.

Closes #695

See merge request !338

This was happening when the remote response arrives before the local
response is made and thus the local response needs to be send with the
ACK following. The problem was that we ACK was sent before the response
which is not allowed and resulted in the session being aborted by the
introducee. This was happening, because recursion is hard ;)

The fix is only restarting another protocol engine to send the ACK
after the first run has been completed.

An integration test was added to prevent such regression in the future
and to test this code path.

Don't show introduction onboarding again no matter how dismissed

Closes #690

See merge request !337

All text that can be generated by users will show emoji from the
shipped sprites.

For all messages and posts, the custom emoji keyboard is now available.

This also disables menu actions rather than hiding them and thus
closes #677

Included is a fix for a regression that was not showing the keyboard
automatically in forums and thus
closes #676

Create PrivateGroupManager Facade and stub implementation

Some classes were renamed and new base classes introduced in the process. I suggest to expand the "Changed files" before reviewing to get an overview over the changes.

Closes #673

See merge request !332

Fix integration tests

First problem was a race condition with message delivery and the second
one due to the fact that we no longer plan to allow adding of additional
blogs, so the test for that has simply been removed.

See merge request !333

Check length of text after spanning

Closes #685

See merge request !334

First problem was a race condition with message delivery and the second
one due to the fact that we no longer plan to allow adding of additional
blogs, so the test for that has simply been removed.

The app _name string is marked as non-translatable and the new_identity_item string no longer exists.