[bug 969667] Replace mobile/desktop forms with generic

* nixes desktop and mobile form routing (yay!)
* replaces that with new generic form
* update tests to denote that we now essentially ignore validation
  errors with email addresses and descriptions--Thanks!
* update ancient android form post handling to also ignore errors
* clean up code after all that
[bug 969667] Clean up CSS/JS

This cleans up some of the CSS and JS after removing the desktop and
mobile feedback forms.