Give Nuance form sources a web UI

Summary:
Ref T8434. Hard-codes form sources as a complaint form.

This form is close to perfect and I'm not actually sure we need to let users customize it at all.

Test Plan:

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T8434

Differential Revision: https://secure.phabricator.com/D13166