Provide a working way to configure the plain xowiki chat includelet: at Chat class instantiation one can now specify a configuration dict that will be persisted in an nsv and used to set option parameters (instance variables) such as login messages, logout messages and the messages time window (and potentially other options in the future). This persistent configuration happpens whenever a client logs in.
Retract configurability for plain xowiki includelet as, without some way of persisisting the conf over subsequent object instantiations, would really not work and also ignore chat room configs