Convert to use formalchemy for all forms

[rgrp]

Current form stuff is not very good (uses formencode). Switch to formalchemy would improve this, especially on validation.

As an extra we could utilize the formalchemy pylons admin interface (pretty much for free).

Cost: 12h

Details

1. Replace htmlfill and formencode extract in controllers/templates with formalchemy
   1. Crude and simple
   2. Suppress unwanted fields (revision, state, all revisions) and sort out ordering to be similar to before.
   3. Sort out tag field with a special renderer
2. Validation - testing definitely required.
3. Fix up description and pretty css etc