navbar: make some changes

fix arrow key alignment in landscape
fix a check in onAttached making the observer attach again
fix alternate IME back key on lockscreen

ps2: use mSettingsObserver's being null to tell if a view is already attached/detached
ps3: restore mSettingsObserver-related stuff to how it was for context stuff and stuff stuff
ps4: fix searchlight and navbar disabling

Change-Id: I2260ad2b8cb7919d6adce8958f4cfcab817552d6
Fix tinting behavior for custom app NavBar icons.

Change-Id: If216dfb39509031f481916f45146d21ef5ec02d6