silly actionbar shadow issue

// FREEBIE
fix AppCompat theme crash

Fixes #2084
// FREEBIE
add "elevation" window overlay for android 4.x too

// FREEBIE
refactor preferences into multiple PreferenceFragments
change textcolors
make "enter key sends" dependent on "enable enter key"
improve push registration behaviour
fix for ringtone selection with android-support-v4-preferencefragment
staying in preferences after enabling passphrase protection