Use plone.formwidget.RecurrenceFieldWidget for recurrence input.
Fix/cleanup field order and javascript.
Use correct start date for recurrence generator.
Update widget configuration.
Make recurrence field optional.
Add new dependencies.
Add validator for additional form-side validation.

The invariant does not seem to work when groups are involved.
Add tests to document defect "isValidOption" invariant.
Add Recurrence to group separately reservable Allocations.
Fix removing allocation entries.
Add tests for removing recurrences.
Add collective.betterbrowser pyquery extra.
Prevent formgroups.js from crashing the whole page.
Fix z-index for nested overlays.
Fix request_id_as_int.
Update .gitignore for buildout in project dir.
Start fixing tests.
Use multiadapter to access widget values.
Use interface when getting multi-adapters.

Conflicts:
	seantis/reservation/form.py
Improve error messages in tests.