Make it easier to add semi-privileged

[bethlakshmi]

Attendees who are key to participation, but not "running" the event are not easily added to the system. We need more ways of adding attendees. Examples:

• Judges for the Main Event should be booked for Main Event only
• Backup dancers and troupes in Acts & Shows.

[bethlakshmi]

Also - heads of everything don't need to have every run of their leadership thingy show up on their schedule. And they should be able to sign up for thier own volunteer shifts

[bethlakshmi]

And we should be able to aggregate roles within an event - for example the tech crew have:

• follow spot
  • stage kitten
  • sound
  • lighting
  • ?general?