UDP Fixes

-=-=-=-=-

Curse the day I decided to port UDP code, as it ended up
being two nights of work.  At least It's done now (I hope).

-Fixed UDP Support, API seems stable
-Added UDP Chat demo (chat that can lose your packets, heh)
-Added helpers to areas and bodies to get list of collided bodies and contained bodies.
-Sped up screen/viewport capture code.
-Added code to save an image as PNG
-Small fix so scripts register their singletons after modules did.

modules/gdscript/register_types.cpp

@@ -125,7 +125,7 @@ void register_gdscript_types() {
 	ObjectTypeDB::register_virtual_type<GDFunctionState>();
 
 	script_language_gd=memnew( GDScriptLanguage );
-	script_language_gd->init();
+	//script_language_gd->init();
 	ScriptServer::register_language(script_language_gd);
 	resource_loader_gd=memnew( ResourceFormatLoaderGDScript );
 	ResourceLoader::add_resource_format_loader(resource_loader_gd);