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
(cherry picked from commit 28ca0be67431abd1ecb3093a1dbe11fe648317c0)