Access Control for Events

Add "An Event" as a type of data in the "Manage Extended ACLs" form and implement code to permission access to Event Info and Event Registration based on ACLs.

As with Profile ACLs, the View and Edit 'operations' will have the same meaning for this implementation (either one allows associated Role to register for the event). If folks bring us use cases for having separate permissions for "viewing Event Info" and "Registering for an Event" - we can look at adding this granularity in the future.