Object table remove (#139)

* Object table remove redis module

* Test case for object table remove redis module

* Client code for object_table_remove

* Delete object notifications in plasma

* Test for object deletion notifications

* Fix subscribe deletion test

* Address Robert's comments

* free hash table entry

src/photon/photon_algorithm.h

@@ -70,6 +70,15 @@ void handle_object_available(local_scheduler_state *state,
                              scheduling_algorithm_state *algorithm_state,
                              object_id object_id);
 
+/**
+ * This function is called if an object is removed from the local plasma store.
+ *
+ * @param state The state of the local scheduler.
+ * @param object_id ID of the object that was removed.
+ * @return Void.
+ */
+void handle_object_removed(local_scheduler_state *state, object_id object_id);
+
 /**
  * This function is called when a new worker becomes available
  *