form_extras.py ("field" template tag) supports values stored in JSON fields

Also:
* misc. support for admin site
* recover from merge
DRY out use of JSON error return utilities

* Move JSON error return utilites to util.py
* Fix a bug in field/ul.html template
* Fix URL in browseTreesMode.js
inlineEditForm.js no longer requires endpoints to include "ok" or "error" in returned JSON

Also:
* Fix lint
Use DotDict.py for stronger JSON field access

Also:
* Switch to "instance.config.foo.bar" (instead of "instance.config|foo|bar")
* Tweak to inlineEditForm to help debug errors