Fix 2538826: Allow aspect of LockPatternView to be customized.

This fixes a problem where the pattern unlock area shrank on
mdpi devices.

This change is required since some devices (mdpi) don't have
enough vertical room to show a square LockPatternView and shrink
the area to match the minimum of width and height. To fix the
problem and minimize changes to existing platforms, the parameter
is configurable and has a default in values/donottranslate that
emulates the old behavior.  New behavior for mdpi devices is
specified in values-port-mdpi/donottranslate, which is the
only place we currently see the problem.

Tested:
mdpi device in both orientations
hdpi device in both orientations
hdpi device in both orientations with keyboard open/closed

Change-Id: I3b9a5ef1d9b5e70f7b1823c9f48a3938f52cc7a4