Missing edge listeners

[rafal-software]

My suggestion is to add edge listeners.

[rafal-software]

I`ve added the listener - one general listener for all edges the same approach should be implemented for node. Currently it is easy to add this listener to current listeners doubleClick example below:

    addFunction(Constants.ON_DOUBLE_CLICK, new JavaScriptFunction() {
        @Override
        public void call(final JSONArray properties) throws JSONException {
            DoubleClickEvent event = EventGenerator.getNodeDoubleClickEvent(properties);
            if ((event.getNodeIds()==null || event.getNodeIds().isEmpty()) && event.getEdgeIds() != null && !event.getEdgeIds().isEmpty() && edgeListener != null) {
                edgeListener.fireEdgeListener(event.getEdgeIds().get(0));
            }
            fireNodeDoubleClickEvent(event);
        }
    });