Moves code for updating MNO's delta since the use of intervalWasAdded hindered the update in some cases where an endpoint was not included. The MNO is still not properly maintained!
Cleans up IBS AVL a little bit
Updates MNO so it works for intervals that are not inserted. It searches for the splitnode and then the endpoints, updating MNO on the way back if necessary. It won't update if interval was not inserted, and only call the update function, when the value actually needs updating.