This allows for situations where one has a comet-master-server which book-keeps a list of servers (typically in a Map) and one wants to remove the comet-server from the map when no more listeners are present.
(In [[r:ddf1cb844898181341ecb2d7b5050a8cdfae5a6f]]) Closes #1140 Added onListenersListEmptied() to ListenerManager to be able to react when listerners-list is emptied
Imported from Assembla: http://www.assembla.com/spaces/liftweb/tickets/1140
Closes #1140 Added onListenersListEmptied() to ListenerManager to be …
…able to react when listerners-list is emptied