[bug 1086643] [bug 1086650] Redo infrastructure for product picker version

This redoes the infrastructure for having the generic form and the
product-picker version of it "live" simultaneously.

* nixed all the extra routing in favor of a waffle flag "feedbackdev"
* extracted product-picker specific unit tests and put them in their own file
* wrote a with_waffle class/function decorator that lets us more easily
  test waffley things
* added WAFFLE_OVERRIDE=True to settings--we always want to be able to
  explicitly set the waffle flag via the url
* added smoke tests for the dev form and product picker page
Fix backwards migration
Merge pull request #368 from willkg/1086650-redo-picker

[bug 1086643] [bug 1086650] Redo infrastructure for product picker versi...