Wsadl - WebSocket application desciption language

- initial minimal @Beta version
- exposes only endpoint paths
- @see TyrusWebSocketEngine#WSADL_SUPPORT
Refactoring:

- TyrusWebSocketEngine: removed constructors, added builder
- TyrusServletFilter: removed ctor with ApplicationEventListener, added getter to TWSE.
- (Tyrus|Cluster)Session toString()