OmniSwitch: Immersive mode button

PS13:
-make image a little bit smaller to match the rest
-cleanup

PS14:
-more cleanup

Change-Id: Ief338c252f0c7b9819040a48cc374d1f208854cc
Merge pull request #1 from omnirom/android-4.4

OmniSwitch: Immersive mode button