Add a mechanism to prevent writing to the Object Graph when it is saved.

[zdenek-jonas]

Currently, problems can occur if the object graph is modified by another thread at the time it is saved. This can occur when using e.g. MVC frameworks, when several parallel requests cause writing to the object graph.

The suggestion is to add a mechanism that will process and save these changes to the object graph sequentially in the queue so that no change occurs when the change is saved.