Move preferences:

Category Interface:
- Add "Bars" header
- Move "Statusbar" header to "Bars"
- "Statusbar": Add "Gestures" preference screen
- "Statusbar": Move "Brightness control" to "Gestures"

Category Device:
- "Display": Move "Double-tap to sleep" to "Statusbar" -> "Gestures"

Change-Id: If0dbf68bc64f82537f6bbb68f56e8a27c2e7ae12