Fix: Remove unclosed and unnecessary form->create() call

The presence of the form tag was causing the first delete link in index
not to work.

See: http://croogo.lighthouseapp.com/projects/32818-croogo/tickets/482-taxonomyterms-cant-delete-first-term-in-index#ticket-482-4

Closes #482
Fix: Avoid `ambiguous column` errors

This might happen if a behavior 'injects' a relationship.
Make the field explicit by passig it through escapeField()