more code to delete, we don't need to create apps from AMO
add a test to stop future breakage (bug 882163)
Add SIGNED_APP_* settings to stage (bug 877531)
Revert "Merge pull request #803 from ngokevin/themethumbnails"

This reverts commit 84c82ea4082718a7d6d76dfa01172e724b271729, reversing
changes made to fe1e96951a54e330327bd025123f8e1dbbf0a347.