Experiments in IPC for my elucidation

I'm going to go with unix datagrams, because they don't
 have nasty corner cases--like blocking at open() or select()
 *not* blocking at EOF--to work around.
internal Changes client class (untested)
INSTEAD OF experiment
Clean up the non-experiment version enough that it will load into the DB.
Internal "Client" sub-unsub stubs (untested)
stub out internal-client registration

Using GUIDs for good measure
And this now--as expected--hangs when tested with a naive execute() (e.g. via psql),
because the spooling never ends but execute() buffers the entire result before returning.
This also hangs because I haven't written the actual broadcasting yet.
It also hangs because