Bugfixes:
- Fixed a bug where attendee passwords weren't saving, and passwords weren't being checked for uniqueness, which meant that one attendee with a blank password ended up removing all other attendees with blank passwords
- Fixed some frontend JS errors
New features:
- A 'subscribe to event group' button which allows users to receive notification of new events by email
- An (experimental) ICS calendar feed URL for event groups which allows calendar apps to sync to new event group events