Wi-Fi: Manage Wi-Fi AP priorities

AOSP has a basic LRU priority for Wi-Fi networks (last connected has
more priority).
This changes added the ability of graphically set the priority of any of
the configured
Wi-Fi networks through Settings -> Wi-Fi -> Advanced Settings -> Wi-Fi
priority.

Port from cm-10.2:
* Added ic_grabber icons

Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Signed-off-by: Michael Bestas <mikeioannina@gmail.com>