Active display: Enable proximity sensor only when screen is off

This should ease people worried about cpu usage of the proximity
sensor while the screen is on.  The sensor listener will only be
registered when the screen goes off, and both active display and
pocket mode are enabled.  Once the screen turns on this listener
will be unregistered so no further updates are received when the
sensor values change.

Change-Id: I70979b5931815adb74bd8bc42e32886a6d829a12
Revert "Active display: Catch Resources.NotFoundException"

This reverts commit d02b8944c02edcfda010adb038f201a03c1d6a00.
Active display: Use a default notificaiton icon.

Change-Id: Iccc25efe943c0b31d405aa49580fb44c5b32a51d
Signed-off-by: scott <scott@ubuntu.com>
Active display: Only fetch next notification if mNotification is null.

Change-Id: Ife8511d4a4b8c448bc7aa8997a250068bec5fae7
 Active display: Catch Resources.NotFoundException
Signed-off-by: scott <scott@ubuntu.com>

Change-Id: Ic9b44146b8c932c519278ceb21242c20ca3c8310
Frameworks: add never sleep screen mode (1/2)

to qs ScreenTimer Tile
to PW ScreenTimer toggle
as general option as well

Change-Id: Ic78356c1b96044562efbce3cb0d0d5c93d773a19
Signed-off-by: scott <scott@ubuntu.com>

Conflicts:
	packages/SystemUI/res/values/slim_strings.xml