Controllers: Field-level template overrides

[loppear]

Currently you can override

• The entire template/form for a model
• The rendered partial for a given form input type (string, json, etc)

It would be nice if you could:

• override both display and input with rendered partials on a field-name basis
• equivalently, define new semantic field types (this and that "json" fields are really geojson), on top of WL's type information.

Probably this should also interact with better field-level validation / form library.

Particularly want these for specifying a map display and map editor, would also let us specify whether a given array field should be edited as json, comma/newline separated, a rich tag UI, etc.