Add some small stuff to support the current implementation of the plab
evproxy, which uses set_failover and set_connection_retries. The event library had these as noops, so that was an easy change. Also, add back in the async add/remove subscription stuff, which was already implemented in pubsub but not hooked up from the event library. In the tmcd/plab directory I purged all mention of elvin and changed it to "event server". I also renamed the runelvin script to runevents. In events/proxy I cleaned up the makefile and added evproxyplab to the targets list since it should now build okay (no longer needs to link against elvin stuff). Renamed elvindtest program to eventping, and otherwise purged lots of "elvin" tokens.