WebSockets support for IDE

[delchev]

Better responsiveness for the IDE e.g. debug.

[ThuF]

Execution flow:

1. From the client-side JavaScript, register the according Java "ServerCommunicationProcessor".
   1.a) Call server-side JavaScript file, that will create an instance of "ICommunicationProcessor" (interface containing onOpen(), onMessage(), onError(), onClose() and getId() methods).
   1.b) The JavaScript file, should register with the ID (getId() method), the created instance into "Processor" collection.
   1.c) After the registration of the "ServerCommunicationProcessor", call "/communication" endpoint and send the ID of the "ServerCommunicationProcessor"
2. The "/communication" endpoint should retrieve the "ServerCommunicationProcessor" from the "Processor" collection and dispatch the incoming requests to the appropriate methods (e.g. onOpen(), onMessage(), onError(), onClose())