better exception handling, including generic error message on client, and catching all uncaught exceptions on server (so we don't crash), and also fixing bug in nodeutil's "promise" related to exceptions (namely, if a fiber has unravelled because of an exception, then callng "run" on it used to restart it, which is bad, we really just want to "continue" it where it left off, not restart it, so if it crashed, we want to leave it that way)