Add xxhdpi check drawable for notifications

Fixes blurry mark as read icon on Android Wear. FREEBIE.
Merge pull request #1678 from veeti/check-icon

Add xxhdpi check drawable for notifications
use latest android number as recipient number

Fixes #791
// FREEBIE
Update language translations.

// FREEBIE
Bumping version to 2.1.0
Upgrade to latest Android gradle plugin

// FREEBIE
Closes #1660
Add date to saved media filenames

Fixes #1689
Closes #1693
Add number of messages to the notification number attribute

Although not used by stock Android, many custom ROM's (and possibly OEM
versions?) have a setting to display the "number" count of a notification
overlayed on the status bar icon. Add support for this.

Closes #1637
Create a Curve25519 asymmetric master secret for users without.

Fixes #1701
Bumping version to 2.1.1
transport selection rewrite

// FREEBIE
use send button as indicator, no auto send
dark theme.
tweaks and cleanup
renaming
remove inefficiencies in transport select
another rename
Made transport selection persistent.
Added SMS / PUSH transport labels to incomming messages
Added a preference to control incoming message transport type preference