keyguard: fix layout for sw320dp devices

800x480px dpi devices have less screen space than the xhdpi devices
Google designed the layout for and the layout needs adjustment.

- Reduce the lockscreen security container size such that the clock
  widget has enough space to display its content.
- In the SIM PIN/PUK view, Google put an empty widget on top, but
  we don't have space for that, increase its size such that the
  widget practically disappears.

This should not have any effect on devices with larger screens.

Ported from cm-10.2.
* Removed invalid mdpi layout leftover from framework-res
* Fix keyguard for mdpi devices too

Change-Id: I9e811cfd312abae24a9cad189d19e73848f6c4c1
Fix a bootloop problem when /data/system/usagestats/usage-history.xml is empty.
This often occurs after an incomplete reboot/shutdown or battery pull.

Change-Id: I4f01151f4051df4ae1b85fa460ec7a9e70122878