Simple Empty State Messages

This MR implements very basic and simple empty state messages for the
current features.

This is how it looks (note that the contact add FAB will be removed soon):

![Screenshot_20160629-125146](/uploads/4c6a8be041cc48b0aba165dd507453d5/Screenshot_20160629-125146.png)
![device-2016-06-29-130834](/uploads/821677074d7d3e6435574a0711f3a0a7/device-2016-06-29-130834.png)
![Screenshot_20160629-125138](/uploads/a39a465db51f8e009ab0b6ee34d4a7e7/Screenshot_20160629-125138.png)
![Screenshot_20160629-125853](/uploads/1dab114bbe7ba379b20a5d298c8fa25c/Screenshot_20160629-125853.png)

Closes #327

See merge request !236

Removed the Fab and moved the icon into the toolbar

Closes #449

See merge request !240

Hide Identity Selector When Adding Contact

Closes #452

See merge request !233

Update Timestamps Every Minute

Yes by using `notifyDataSetChanged()` I am invalidating everything, but view binding is very fast and the RecyclerView is smart about it. I could parse the dataset and use `notifyItemChanged()` only on the elements that matter, but this is not generic and a lot more code which is not necessarily faster. I suggest we go with my simple and generic approach for now and optimize when we actually notice a performance problem.

Closes #455

See merge request !238

Closes #452

Closes #455

Blog Client Unit and Integration Tests

Closes #450

See merge request !230

This implements very basic and simple empty state messages for the
current features.

Closes #327

Font Colors and Separate Themes

Once applied this commit will change the font colors according to the
design and move all themes into a dedicated file.

Closes #333

See merge request !228

Remove unused Java layout helpers

Closes #397

See merge request !232

Closes #397

Make timestamps prettier and more useful

Here's some example timestamps I have been testing with. That's how it will look like when this MR is merged:

![device-2016-06-28-184748](/uploads/c082ac0f54b50c27f9a1c5ef8865998b/device-2016-06-28-184748.png)

Closes #230

See merge request !235

Trim leading and trailing whitespace when displaying messages

Closes #326

See merge request !234

Closes #326

Once applied this commit will change the font colors according to the
design and move all themes into a dedicated file.

Closes #333

Closes #450

Deduplicate contact exchange protocol

`ContactExchangeTask` was originally extracted from the Bluetooth invitation task; this completes the refactoring.

Closes #365.

See merge request !199

Make use of Existing Translations

Adds first translations to source code and sets up transifex config
file. Pull more translations later with:

```bash
 cd briar-android
 tx pull --mode=developer
```
Closes #448

![device-2016-06-23-145337](/uploads/14c557adf185dce516ca94295b4db965/device-2016-06-23-145337.png)

See merge request !226

Adds first translations to source code and sets up transifex config
file. Pull more translations later with:

 cd briar-android
 tx pull --mode=developer

Closes #448

Merge branch '442-author-s-identicon-nickname-and-status-are-separated-in-forum-post-layout' into 'master'

Separate Date and Author Name in Forum Posts

This also fixes the issue there the trust indicator was shown at the top on some devices.

![device-2016-06-23-152315](/uploads/62786502942bbccadf809fedd72cedd1/device-2016-06-23-152315.png)

Closes #442

See merge request !227

Fix IdentityManager hooks

This commit makes sure that there is only one identity manager that is
initialized early enough so hooks can be added properly.

Closes #446

See merge request !225

ContactExchangeTask was originally extracted from the Bluetooth invitation
task; this completes the refactoring.

Closes #442

This commit makes sure that there is only one identity manager that is
initialized early enough so hooks can be added properly.

Closes #446

Backend for Automatic Micro Blogs

This MR introduces automatic personal blogs to the Blog client. When a contact is added, her personal blog will also be added automatically. Also, when a new identity is added, a personal blog for that identity is created.

The first commit changes the blog paradigm to short-form blogs and introduces other things that will be useful later in the UI (!214) such as a BlogPostAdded event and the possibility to delete/remove blogs (not the personal ones).

This MR is based on !224 to prevent crashes that are fixed by it. So please review and merge !224 first.

See merge request !223

This is useful when sorting blog posts in the combined feed. It ensures
you do not miss older posts that were just synced to you.

When a contact is added, her personal blog will also be added automatically.
Also, when a new identity is added, a personal blog for that identity is created.

Part of #436

Removes teaser and makes body mandatory.

It also adds support for deleting blogs and
introduces a getAuthorStatus() method to the IdentityManager
that takes a running transaction.

Remove MAX_GROUP_DESCRIPTOR_LENGTH

Closes #441

See merge request !224

Closes #441

Forum improvements

Forum Activity improvements:

* Orientation changes now restore the activity properly, e.g. input text and state is retained
* Snack bar is now, when appropriate, clickable
* The bottom divider is no longer visible for the bottom entry
* Code refactoring for improved simplicity and less redundancy
* Timestamp check to ensure that new posts are not older than the latest post

Closes #426 
Closes #423 
Closes #424 

See merge request !218

Fixing fragment instance restore

Alas, it turns out that my neat way of integrating the Fragments into the dependency graph was not without problems. Me and @grote discovered that this presented us with a lot of problems on orientation changes as the Activity is re-created, and therefore parts of the dependency graph. The simplest solution was simply to abandon the idea, i.e. with this branch Fragments are no longer part of the dependency graph. 

See merge request !215

synched conversation and forum input

Closes #354

See merge request !219