Set listener properties for UMS mount/unmount

Some kernels require the usb functions be defined before UMS mounting
of storage partitions will work. This sets the sys.storage.ums_enabled
property upon mount/unmount which can be listened for in init.rc.

Example routines to include in init.rc:

on property:sys.storage.ums_enabled=1
    write /sys/class/android_usb/android0/enable 0
    write /sys/class/android_usb/android0/functions adb,mass_storage
    write /sys/class/android_usb/android0/enable 1

on property:sys.storage.ums_enabled=0
    write /sys/class/android_usb/android0/enable 0
    write /sys/class/android_usb/android0/functions adb
    write /sys/class/android_usb/android0/enable ${service.adb.root}

Change-Id: I8a8ad4b392abbaa173d402714bcb4049ba84ccca
Force GUI render after setting brightness

Change-Id: I4470a3a090d10f400575d45338a8349fbee8a027
minui: Allow devices to blank/unblank using LCD backlight

* Some devices rely on the LCD backlight to blank/unblank the display,
  support them by allowing a custom LCD backlight path to be used.

Change-Id: I8406b4b55cd7a2afc4f8f8ba65de2c53b949489d

Conflicts:
	minui/Android.mk