More visual script work

-Block switches to 2d/3d editor if editing visual script
-Added cast node in flow control
-Added ability to do RPC in visual script
-Comment nodes
-Fix bug with inverted cable in connecting backwards
-Copy and paste nodes, including from different scripts

core/script_language.cpp

@@ -33,6 +33,7 @@ int ScriptServer::_language_count=0;
 
 bool ScriptServer::scripting_enabled=true;
 bool ScriptServer::reload_scripts_on_save=false;
+ScriptEditRequestFunction ScriptServer::edit_request_func=NULL;
 
 void Script::_notification( int p_what) {