Bug 861994 - import Gecko resources and fix theming

This effects minimal changes to be able to apply Sriram's patch.  I cherry-picked just enough pieces of Gecko's styles (and removed some pieces) in order to get things running.  I considered importing all of `mobile/android/base/resources` and updating our scripts, but I decided to leave that until "next time".  (If we do that, there are issues with Fennec putting `.xml.in` files in the `xml/` directory that will need sorting out.)  Just wanted to keep everyone in the loop about these changes before committing.

@rnewman, comments?  I intend to merge this by tomorrow EOD unless I get strong negative feedback.