Add update_uris method and event

Add a way to send mapper updates between client and server and a way
to map between client and server types.

pinos/server/client.c

@@ -106,6 +106,7 @@ pinos_client_new (PinosCore       *core,
   pinos_signal_init (&this->resource_removed);
 
   pinos_map_init (&this->objects, 0);
+  pinos_map_init (&this->uris, 0);
   pinos_signal_init (&this->destroy_signal);
 
   spa_list_insert (core->client_list.prev, &this->link);