[CHORE] Increment build beta number to 4

[FIX] batch of crash fixes from beta3

Use retryIO to retry client calls (still missing on some places)
Better error logging
NPE fixes.

[NEW] Add the possibility to change own status.

[IMPROVEMENT] Keep message on the text composer on fail to send message

[FIX] Blank screen.

[CHORE] Increment version to beta 3

[NEW] Add register username screen

[FIX] Don't crash on missing Play Services.

[CHORE] Increment version to beta2

[FIX] Crash on ViewModelMapper

https://fabric.io/rocketchat3/android/apps/chat.rocket.android/issues/5ac2a7da36c7b235275e002c?time=last-twenty-four-hours

[CHORE] Increment version to beta1 & 2001

[FIX] Alerts the user about username creation using the web version.

Merge branch 'develop-2.x' of github.com:RocketChat/Rocket.Chat.Android into fix/oauth-crashes-when-using-new-user

[FIX] Logout on invalid token.