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
emojicons

// FREEBIE
always show enter key, better minheight
add pin, refactor keyboard height calculation
remove unnecessary invalidate