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.

Change-Id: I0091fa99fd00febddbde820feaae9457a9b8a45f