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* Make `Field` shortcuts compatible with subclassing. Previous fix didn't work all the way.
* Use the new major tri.declarative, and update to follow the new style of class member shortcuts
* Major fixes to how `from_model` works. Subclassing `Form` and `Field` now works like you'd expect. This is a breaking change.
* Removed `Field.comma_separated` shortcut. This was never used, and poorly tested.