fixed bug in validation.validate() to return array if parsing fails

also added a couple tests
removed repeatable flag from registrations transtion.

also removed !doc.patient_id filter. so registrations can run on form
that set the patient_id.

removed the filter tests, since they are not very useful anymore.  we
might consider moving some of the triggers to transitions, just not sure
how yet.
fixed bug in muting function, added `next_msg` variable to regisration
msg context.

only set muted value on scheduled tasks, leave other states
unchanged.

added next_msg variable to message context on registrations.

removed registration_response from scheduled reminders config.  specify
messages on registration config instead.  messages are only sent out
after events are completed so message context will include data from the
scheduled_tasks object like `next_msg`.

modified `registered_patients` view to only include docs that have a
successful registration transition.