Navbar customization in tabletui (WIP)
Again, everything cherry-picked from AOKP
Commits: https://github.com/AOKP/frameworks_base/commit/7c4b367866edf167942b0b743b40a259f381b1d9 and others

Not working:
- transparency and color in lockscreen
- idem when the keyboard is present

Change-Id: Ic279852ef55461d0d82dac50e1e34fa176c8faea