1077423 overhaul generic

TOTAL GENERIC FORM (DEV VERSION) OVERHAUL!

This is a big change. To see it in your browser:

1. do `./manage.py runserver`
2. visit `/feedback/?feedbackdev=1`

To review:

1. check out the CSS--it's a completely new file, so don't bother looking at the diff. does it look ok? am i doing dumb css things?
2. check out the js--i reused a bunch of stuff, so i'm feeling pretty ok with this.
3. check out the html template--does it look ok?
4. run the tests.
5. run the smoketests if you can.
use mixin