Simple reports

[cecilia-donnelly]

@pjsier suggested splitting these out from #309, since they'll be faster to handle:

• Participant results should include total # of actions that each participant in the result set attended

• Action results should include:

  • total # of participants per action
  • total # of unique participants across all actions in the result set

• Filter on the number of actions people have attended in a time range:

  • # people with 1 attendance
  • # people with 2 attendances...