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

...on

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

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The text that was originally here was all moved to `fjord/feedback/templates/feedback/generic_feedback_form.html`.