Move RRULE into Instance, fix Event.compare_to(), Instance.equal_to()
Better solution to master/generated instance problem

All masters are now loaded in the backing and associated with their
generated instances before being injected into the system...this
alleviates I/O and async issues in the UI, who always have access to
the masters by virtue of having access to their instances.
Getting close, can create and update recurring events, still some
work to be done to clean it up and bullet-proof it.