ListenerInterfaceRequestHandler simplification

Branch "request_listener_simplification" contains a proposal to simplify ListenerInterfaceRequestHandler.

By limiting components and behaviors to implement a single callback only, we can remove the identifying part "I*Listener" from URLs.
For page 0, renderCount 1 and behavior 2 the following componentInfos:

0-1.ILinkListener-link
0-1.ILinkListener.2-link
0-IResourceListener-image
0-IResourceListener.2-wmc

... become:

0-1.-link
0-1.2-link
0--image
0-.2-wmc

This format could be further improved, suggestions are welcomed.

This has the following advantages:

• framework exposure in URLs is minimized
• URLs get shorter
• no need to register INTERFACE constants any longer
• instead using of reflection ListenerInterfaceRequestHandler can call a single method on the component or behavior, which makes debugging easier.
• a single interface for components or behavior is enough to be targeted by requests:

	public interface IRequestListener extends IClusterable
	{

		/**
		 * Does invocation of this listener render the page. 
		 * 
		 * @return default {@code true}, i.e. a {@link RenderPageRequestHandler} is scheduled after invocation 
		 */
		default boolean rendersPage()
		{
			return true;
		}
	
		/**
		 * Called when a request is received.
		 */
		void onRequest();
	}