[1.6.8] Transfer transactions should be linked

Currently transfers create two separat transactions. If you need to change something on this transfer, you must do the change in both transactions, because there is no link between those transactions.

At least a link in the data to jump from one transaction to the other would be nice. Even better would it be, if I could do the change in one transaction and the changes are broadcasted to the other transaction. => Counter entry ("Gegenbuchung") Button