Make post forms programatically generated

[teodesian]

Right now the templates and filters are in two places:

• The form itself
• Trog::DataModule

We need the form to have some means of self-describing where it tells us what parameters to filter from being stored, and what parameters it actually expects to have. Then we just change it in one place and there is no source of bugs here.

[teodesian]

Ideally, this is a part of the parent series form.

We could even store these forms in the post itself rather than in www/templates/html/components/forms.