Updating topic behavior

Topics no longer use a straight topic string match and now use
regular expressions.  Currently this code is untested and the
tests are obviously out of date.

Also a bunch of documentation was added to make the design goals
more clear, and to reflect the direction that topic routers are taking.
Registry stub added, and Room routers as well

The stub for the actor registry has been added, this will definitely
change to use a new abstract interface for Actor / Sender etc, but
the goal is to get this working as soon as possible so the remaining
use cases can be worked out.

Room routers are now also mostly functional but untested and well
documented in terms of the design goals.  Rooms provide inexpensive
fanouts to groups of Actors.  At some point, it will need to undergo
a conversion like the Registry (once finished), Topic routers, and
the like.  Actors may end up becoming interface types entirely to
accomodate the collection of things that respond to messages and send.