add RTL support to manifest

Should enable layout mirroring for RTL languages on Android 4.2.
http://android-developers.blogspot.com/2013/03/native-rtl-support-in-android-42.html
Update build target to rev 17 (needed for RTL flipping)
LTR and RTL versions of standard 'send now' action bar icon
Make Android Studio happy with mvn->iml project updates :P
RTL: use start/end properties as well as left/right
Merge pull request #27 from brion/rtl

Initial RTL layout flipping support - plus icon fix for 'send' on 2.3