Merge branch '305-new-forum-list' into 'master'

New List of Forums

The adapter of the `ForumListFragment` has been changed into a
`BriarRecyclerView` and all its code has been adapted and simplified
accordingly.

All UI of the forum list is now defined in XML layouts. This enabled me to move the snackbar into onCreate().

Before:

![device-2016-05-03-165331](/uploads/961cc2c043464f446584de4ae0ad527b/device-2016-05-03-165331.png)

After:

![device-2016-05-03-165117](/uploads/e22ede3e9a3330762b3ae84f86ca6ec5/device-2016-05-03-165117.png)


See merge request !175