fix unsynchronized Action-Callback block
added getFriendlyName method based on a uniqueId
 - works only for websocket, not socketio
 - not the best solution (client generated id) but allows to expose
multiple services
added unexposeService methods, on server side and client side (nsdLib.js
only)
fix issue on connect (nsdLib.js only) in order to expose multiple
services 
fix issue on getNetworkServices (nsdLib.js only) in order to be notified
of changes in the exposed services list