#969586 Completely refactor the form processing so previews work in overlay. Did a bunch of cleanup in the process, other things may have broken, this will need some shaking out.

Trying to figure out how to get the list of date fields back into the date argument and filter. Something must have changed.

#935076 Add tests, including one provided by tristanoneil, plus a few fixes uncovered by the tests. More tests coming, this is a start.

#929494, Got an ISO date with select widget working correctly with proper timezone conversions after implementing new FAPI workflow. Now need to get other field types working and add tests.

More clean up of formatters and formatter settings, more re-organization to make the code easier to maintain.

With new formatter settings we can simplify date formats. Make the format type a setting instead of having different formatters for each type. We can also add settings for the interval formatter later.

Re-organize all the field hooks into a single file and add the formatter settings form and summary. This will probably see more changes, this is a first pass.