Themes: Add versioning to the theme feature

As new features and enhancements to the theme apk format are added
we will need a way for themes to specify which version of the theme
format they are targeting.  Exclusion of the theme feature in a
theme apk will imply v1.

Change-Id: I0016d58341ca3144bb4a4faa16663ab29439ab24
Merge remote-tracking branch 'ap/kitkat' into kitkat