parmdb overhaul. support collection add/del
sync when host comes back online. use udp not tcp.
host #0 can now handle a new incoming request while
a parm change is currently outstanding.
all missed "command" parms will be received when a dead host
comes back online, too, like a tight merge for instance.
does not use msg4, uses msg3e and msg3f for syncing and
sending parms.