Work on main loop

Make a main-loop object with associated helper functions to handle async
methods.
rtloop -> data_loop
Handle async results a lot better.
Remove REMOVE_MEM command. We don't need it.
Handle stream memory updates better.

pinos/gst/gstpinosdeviceprovider.h

@@ -82,7 +82,7 @@ struct _GstPinosDeviceProvider {
   gchar *client_name;
 
   GMainContext *maincontext;
-  PinosMainLoop *loop;
+  PinosThreadMainLoop *loop;
 
   PinosContext *context;
 };