Better layouts for security screen setups as part of b/7459863

The major change is that choose pattern and confirm pattern layouts
no longer uses a split screen layout on tablets.  The new layout
closely mimics the layout for portrait.
Other minor changes include:
-Made the header font size for confirm pattern and choose pattern
medium (this matches with face unlock changes).
-Made the buttons on choose pattern for landscape phone side-by-side
rather than above each other (to be consistent with face unlock).
-Removed the black background from phone landscape confirm pattern
since it's inconsistent with all the other layouts.

Change-Id: I4473fe880ac471a3b5bc5399a454b10504589f87