work on memory references

Add a memory reference helper struct that we can use to track the memory
in buffers and formats.
Remove custom property get and set, the default ones will work fine.
Custom ones are problematic when we want to serialize properties in
formats etc.
Deserialized Formats are now tracked in the memory pool and can be freed
if needed.

pinos/client/stream.c

@@ -600,6 +600,8 @@ parse_control (PinosStream *stream,
         priv->format = g_bytes_new_static (str, strlen (str)+1);
         g_object_notify (G_OBJECT (stream), "format");
 
+        spa_format_unref (p.format);
+
         /* FIXME send update port status */
 
         /* send state-change */