[bug 913613] Implement new Firefox OS feedback form

This form differs from the existing mobile feedback form in that it has
two additional fields that are Firefox OS specific.

This form submits data using the Input API.

This requires some Selenium tests, but I'm landing it now so it can
get a UX/UI pass. Once I get the ok, then I can upload strings for
translation. Then I'll backgrack and work on Selenium tests to cover all
the possible flows.