Fix site so there is no more admin login page

If you logged in with persona, went to the admin, then clicked on
"logout", you'd end up on the admin login page which you had
to manually leave by typing a url in the urlbar.

This fixes that.
[bug 832569] Support Firefox for Android

* add two fields to the Simple table: device and manufacturer.
* tweak _handle_feedback_post so that it knows about _type which is
  the old way of doing things
* tweak the mapping code so it's easier to read (it's probably not the
  best idea, but it is easier to read)
* add a bunch of tests