Suggested improvements to Canvas Conference’s Interface

Suggested code for issues:

https://github.com/instructure/canvas-lms/issues/529
https://github.com/instructure/canvas-lms/issues/530
https://github.com/instructure/canvas-lms/issues/531
https://github.com/instructure/canvas-lms/issues/534


I take it this is all redefined here because if we `set_policy` at all in the subclass this the `set_policy` block of the superclass doesn't enter into it.

I'm struggling with the code duplication, though. Is there a way we can avoid that? Perhaps rejigger the `set_policy` block in the superclass to cover the cases in question here?