When retrieving an object from DB4O by default it will pull across all related objects down to a depth of 5. Clearly this may have an impact on performance for large graphs and so we should allow the "maxFetchDepth" in the FetchPlan to be used to pass through to DB4O. Also need to test the activation process for when an object is accessed at the edge of the DB4O graph and is returned initially "deactivated". When accessing the field (and hence calling storeMgr.fetch() the object should be activated, so need to test that it is