Status and nav bar customization (2/2)

- Status bar transparency
- Status bar colors
- Status bar transparency mode
- Nav bar (enable/disable)
- Nav bar dimensions (height, height in landscape and width)
- Nav bar background (color, transparency and transparency mode)
- Several changes in SystemSettings.java, by me, to enable navigation bar in devices with hardware buttons and also show all expanded desktop options

Change-Id: Iafccd6cb0a1bbd4b2d8e0d53f495cf8464722a65