The switch to having a function in Managed_DataObject is now being applied
to plugins which can use this as well.
There are some plugins that still use Memcached_DataObject, but these will
be taken care of later.
A bunch of the common_* functions for date formatting expect an interpretable string, rather than a Unix timestamp, as input. Switched to using the DB-formatted timestamps as we put them into the object rather than the unix timestamp intermediate value when formatting the plaintext and HTML fallback content.
* RSVP cancel/delete now works
* caching fix for RSVP insert and delete (compound unique keys aren't properly handled for pkeyGet's caching right now; hacked it for this class for the moment)
* div nesting fix
* missing name/avatar on RSVP responses
