Added the base class for the UI controllers and the 1-pane implementaion,
which is almost empty at this point.
The old phone activities still exist and will be used on the phone by default.
To use the new activity (1-pane EmailActivity) on the phone, use the following
comamnd.
adb shell am start -a android.intent.action.MAIN \
-d '"content://ui.email.android.com/view/mailbox"' \
-e DEBUG_PANE_MODE 1
Change-Id: Id1fe85d4517778afc967d7d5e17e1299dd1bfefd
f5492ea991