Remove unused files.

Fixes #1522

// FREEBIE
Replace XML serializer in plaintext export

Fixes #342

- using regex pattern/matcher to escape chars below 0x0020 and
  above 0xd7ff
- using String.Replace to escape XML entities
- changed XmlPullParser from Xml.newPullParser() to
  XmlPullParserFactory parser to fix import on GB
Revert "change out key cached icon to be more unique"

This reverts commit d6d76fa95315068ab5457b23fb4908c4a8586982.
no longer load a recipient for each filter text

// FREEBIE
Merge pull request #1642 from mcginty/canonical-bunk-addresses

don't try to load recipients for each filter text
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
use xstream for serializing
import stuff
xmlbackup correctness
rebase fixes