Make animations more consistent

![animations6](/uploads/0ac694d3561515e04fbb9032d31f183c/animations6.mp4)

Closes #570, #621

See merge request !439

This also removes the BriarFragmentActivity that was only really used by
the NavDrawerActivity.

Add sharing info to ForumActivity action bar subtitle

This indirectly does also most of the work for adding the same information to private groups. However, completing this is blocked by !448.

![device-2016-12-07-152915](/uploads/5bb42f2e78a87931b0307e7597ba72c5/device-2016-12-07-152915.png)

Second part of #646

See merge request !451

Add blog sharing information to toolbar subtitle

This MR introduces a new `SharingController` which is supposed to be used in activities that show blogs, groups and forums. Feedback on this approach is welcome before this is used to add "Shared with" support to other parts of the UI.

The toolbar subtitle shows information about how many contacts the current shareable is shared with and how many of those are online.

So far this is implemented for blogs:

![device-2016-12-05-180207](/uploads/13afb4c7c5d10ad29c414865ee02670d/device-2016-12-05-180207.png)

One part of #646

See merge request !447

Add unit tests for PeerProtocolEngine

Although not all classes have unit tests, this

Closes #766

See merge request !450

Add unit tests for InviteeProtocolEngine

Next part of #766

See merge request !444

The toolbar subtitle shows information about how many contacts the
current blog is shared with and how many of those are online.

Fix Sharing Status screens

* Remove distinction between "shared with" and "shared by"
* Show all contacts a blog is shared with
* Show online status of contacts in sharing screen

![device-2016-12-05-142949](/uploads/703fbd2d52815374e57edd89f754bf6c/device-2016-12-05-142949.png)

Closes #810

See merge request !445

Remove verbose logging from introduction client

Closes #808

See merge request !449

Introduce Dialog Theme for Onboarding

Currently onboarding dialogs and confirmation dialogs look the same. This MR introduces a new dialog theme for onboarding dialogs that looks like the tap target onboarding, so that the user can immediately spot the purpose of the dialog.

![device-2016-12-06-085539](/uploads/6d75b17c0f20028bb7ffac65e6fba03a/device-2016-12-06-085539.png)

See merge request !446

* Remove distinction between "shared with" and "shared by"
* Show all contacts a blog is shared with
* Show online status of contacts in sharing screen

Require a label for hashing

* Add a string label argument to `CryptoComponent#hash()`
* Convert `DoubleDigest` from implementing `MessageDigest`
  to implementing `org.spongycastle.crypto.Digest`
  (we need to keep `DoubleDigest` for `FortunaGenerator`)
* Convert all other uses of `MessageDigest` to `CryptoComponent#hash()`
* Remove `CryptoComponent#getMessageDigest()`, `MessageDigest` and `DigestWrapper`

Closes #548

See merge request !442

Ensure key agreement tasks finish if they ignore interrupts

The problem here was that `BluetoothSocket#connect()` was throwing an IOException when the task was interrupted - the task treated this like any other connection failure and retried, so the task never finished.

The fix is to check whether the timeout has expired before retrying, so the task eventually finishes even if it ignores the original interrupt.

Closes #283

See merge request !443

* Add a string label argument to CryptoComponent#hash()
* Convert DoubleDigest from implementing MessageDigest
  to implementing org.spongycastle.crypto.Digest
  (we need to keep DoubleDigest for FortunaGenerator)
* Convert all other uses of MessageDigest to CryptoComponent#hash()
* Remove CryptoComponent#getMessageDigest(), MessageDigest and DigestWrapper

Add unit tests for CreatorProtocolEngine

See merge request !441

Add missing IdentityManager unit tests

See merge request !440

Remove blog pagers

I set out to fix potential race conditions in the blog pagers (the screens you reach by tapping the body of a blog post, that allow you to swipe left and right through the posts in the combined feed or a single blog). The race conditions here are similar to those addressed by !356, but the adapters don't inherit from BriarAdapter so they need to be fixed separately.

While I was looking into this I found a few minor problems with the pagers:
* The feed pager wasn't responding to events - this was fixed in !398
* The feed pager finishes NavDrawerActivity when any blog is removed
* The feed isn't updated when a blog is added (this applies to the list view as well as the pager)
* Posts aren't removed from the feed pager when a blog is removed

The last problem is quite serious - the feed pager's adapter contains posts that are no longer in the DB, so they'll fail to load. To fix that problem, the adapter needs to be cleared in onStop() and repopulated in onStart(). This is the same approach we use for other adapters where items can be removed from the underlying dataset. Unfortunately, FragmentStatePagerAdapter has some odd behaviour when you clear and repopulate it:

1. When reselecting the previously selected item after clearing and repopulating the adapter, the item slides into view instead of just appearing, which makes it look like you've accidentally swiped.
2. Items are sometimes duplicated when clearing and repopulating the adapter, so swiping left or right shows another copy of the same post.

These problems only seem to happen if the adapter is cleared - adding new posts works fine on master, although I think there might be some luck involved - FragmentStatePagerAdapter doesn't seem to be designed to support items changing positions.

I spent a lot of time trying to resolve these problems before concluding that maybe it wasn't worth it, and we should just remove the pagers. That's what's currently implemented in this branch. Tapping the body of a post will show the full-length post, but you won't be able to swipe left or right.

The swiping functionality was nice to have, so if you have ideas for fixing the bugs I'd love to hear them. But I'd rather remove this functionality than keep it in a buggy state with no plan for how to fix it.

Closes #705

See merge request !400