Add support for making form exceptions per category
Add support for making form exceptions per category

This adds support for exceptions to the general form
visibility/requirements per category, and adds exceptions for tag review
and wpt form fields for features in the JavaScript category. This also
fixes a few form visibility issues when editing old feature entries that
don't have an intent stage set.

GoogleChrome/chromium-dashboard,GoogleChrome/chromium-dashboard,GoogleChrome/chromium-dashboard,GoogleChrome/chromium-dashboard,GoogleChrome/chromium-dashboard