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.