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.
Use correct assert methods.
Fix request_id_as_int for negative numbers.
Add Recurrence to group separately reservable Allocations.
Fix removing allocation entries.
Add tests for removing recurrences.
Merge remote-tracking branch 'upstream/master'

Use collective.betterbrowser for tests.
Add collective.betterbrowser pyquery extra.
Add optional plone.multilingual support.
Prevent formgroups.js from crashing the whole page.
Add support for language idependent fields.
Add comment.
Use correct uuid in settings panel.