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

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.