Prevent audio players starting on startup.

Previously, (at least) Apollo was started on startup (in that it
appeared in the notification bar) because it listens to the AUDIO_BECOMING_NOISY
intent to silence itself in that case. This intent is broadcast by
AudioService when there's a user switch to silence any potential audio
players for the old user. As the system also sends around a
USER_SWITCHED intent on startup, this led to the aforementioned player
startup.
As the intent of AudioService was to act on a user backgrounding anyway,
send out AUDIO_BECOMING_NOISY as reaction to a USER_BACKGROUND intent
instead of the USER_SWITCHED intent.

Change-Id: Iba35844a1274c9dd195f104068304e6a7ffa809e
Lockscreen Targets : Make multi-user compatible

Use getStringForUser instead of getString since the framework always run as root user (0)
Navbar : Fix left over glow

Invalidate all buttons, to avoid nearby glow interference
systemui: modify hdpi & xhdpi drawables for battery_min

* These drawables are to large for the new phablet ui. See screenshot:
  http://i.imgur.com/AR8BUH8.png This change modifies the hdpi and xhdpi
  drawables to the sw720p-mdpi drawables, which look correct in the status
  bar.
Volume rocker wake and volume rocker music control