Add routes and tempates for editing msg templates

This adds route handlers as well as phtml templates for the editing of
message templates. None of the logic is hooked up yet, but this is
a good start on the basic UI stuff that will be useful for testing.

Fix a template

It was adapted from the pun creator, so the form was POSTing to the
wrong place. I bet the form element names are wrong, too, now that
I think about it.

Fix the form element names

Becasue they were wrong.