Settings: Navigation bar button color mode (2/2)

due some user complains about the bad coloring of custom and app icons, a fix
became a feature.

- overworked colorizing more icon specific
- introduce color mode (0 = all icons, 1 = only system icons, 2 = system and custom icons)
- change porterduff mode for app and custom icons....now a lot better for most icons
- changed in settings to fit the other structure

cheers

Change-Id: I51847db228f1ff70e9b75201eec78c25f284a4f6