WL-3170 Correct interface for generateEvents
WL-3170 Email cancellation through getter

Adjust the interface for an email to use a getter for the cancellation
status. This is implemented by the subclass and then the subclass can
redefine the cancellation field as required.
WL-3170 Indentation fix
WL-3170 Auto email implements generateEvents

Add a trivial implementation of AutoReminderEmail
WL-3170 Add testing dependencies
WL-3170 Test CancellationEmail

Add a test to see that the Cancellation email type is correctly generating
events.
WL-3170 Test AttendeeOwnCancellation
WL-3170 DRYed out cancellation test code
WL-3170 Test AllUsers type emails
WL-3170 Combine cancellation tests