Fix GLIF pattern for versions < L

For versions < L, setGlifPatternColor should still change the
background drawable, since they are visible on tablets.

Replaced the v21 specific attrs with attribute references in the
themes, removing the need for a separate version attrs.xml.

Moved GlifLayoutTest that doesn't require test XMLs to Robolectric,
so make SDK version testing easier. Robolectric on gradle doesn't
seem to have a good way to include test XMLs, so tests for XML
inflation are kept as instrumentation tests.

Test: ./gradlew connectedAndroidTest test
Change-Id: I36b3765848e462ee920c563a6fa335a0e67dd471