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.

Change-Id: Ief590e799cdb7ef760b631d0b22d9719f867393f
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
add missing icon for lst commit