Get rid of the extended themes.

We now decide whether to use a bitmap background based on whether the
window's drawing is hardware accelerated.  To do this, there is a new
"state_accelerated" that state list drawables can be parameterized on,
and the standard window background uses this to select a solid color
or bitmap drawable as appropriate.

Introduces a little hackery to have wm preview windows pretend like
they are hardware accelerated even if they aren't, so the preview looks
closer to the actual app.

Also Add a DialogWhenLarge variation for the light theme.

Change-Id: I215a79d5df65ba3eed52ab363cade9d8218a6588