Show all Forum Invitations, not only the first one to prevent cut-offs and forks

This MR solves the problems outlined in #461 by always showing forum invitations, even if the user already subscribed to the forum.

Available Forums have been renamed to Forum Invitations in the UI:

![device-2016-07-07-144141](/uploads/9c8d06decdd19117250e3faca0c38192/device-2016-07-07-144141.png)
![device-2016-07-07-144150](/uploads/9803f567c962a721b24d79359974a29f/device-2016-07-07-144150.png)

Closes #461

See merge request !241

Improved the contact addition header

Closes #459

See merge request !245

Set focus mode properly when scanning QR codes

This simple fix contributed by @m8r-v9bo74 fixed the issue on my Xperia
Pro that could never focus on the QR code before. Focusing and scanning
still works on my other test devices.

Closes #346

See merge request !243

Show Snackbar after introduction request has been sent

Closes #360

See merge request !239

Improve Account Setup Screen

* Explain what "account creation" means on first run (#151)
* Use hints instead of dedicated text views
* Move password strength meter up into the user's view
* Always move user's view to current input field
* Improve "Forgot Password" dialog

![Screenshot_20160627-142116](/uploads/7fadc812f62c5f22f6ba73735d139064/Screenshot_20160627-142116.png)
![Screenshot_20160627-142127](/uploads/da27fb864bbe34168665a51b60747181/Screenshot_20160627-142127.png)
![Screenshot_20160627-142135](/uploads/19ddb247a043f56f9429a98e9655cd9f/Screenshot_20160627-142135.png)
![Screenshot_20160627-142153](/uploads/5d859e029a9584598a5cd6a391e697d3/Screenshot_20160627-142153.png)
![Screenshot_20160627-142204](/uploads/f59a79fc30528a17aece31f2c45d4638/Screenshot_20160627-142204.png)
![Screenshot_20160627-142241](/uploads/a493df940ae69b7ae1eecba598b4d378/Screenshot_20160627-142241.png)

Please note that the dialog button colors will be changed in !214 to the official design. Here they have the old colors.

Closes #151, #207

See merge request !229

This simple fix contributed by @m8r-v9bo74 fixed the issue on my Xperia
Pro that could never focus on the QR code before. Focusing and scanning
still works on my other test devices.

Closes #346

* Explain what "account creation" means on first run
* Use hints instead of dedicated text views
* Move password strength meter up into the user's view
* Always move user's view to current input field
* Improve "Forgot Password" dialog

Closes #151

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

even after re-sharing an existing forum.

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 #360

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