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

this commit adds:

- ime switcher notification - thanks cm (NOT ADDED - ALREADY IN)
- slims fullscreen disable on landscape
- slims force autorotation on IME
- volume button control for navigate in the message - thanks cm (NOT ADDED - ALREADY IN)
- 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: I2f7ffba63fa2f0488a6eb282eae53bbdbeccb373