settings: add back all keyboard IME features back (2/2)

this commit adds:

- ime switcher notification - thanks cm
- slims fullscreen disable on landscape
- slims force autorotation on IME
- volume button control for navigate in the message - thanks cm
- slims force to show always enter key

some fixes to the 4.2/4.3 implementations + added full multiuser
support for all this features

cheers

Change-Id: I58596f11ee09c6db77119f3e3044e1ec2dd30c0a
Settings: Add Advanced reboot (1 of 2)

This commit adds a setting in Development settings for including options
in the power menu for rebooting into recovery or bootloader, defauled to
off.
When enabled, the Advanced reboot options will only be available once the
device is unlocked.

Change-Id: I202bf2adec3ba50c1a2e4de2a8f62cdad970ce04