Created new interface ExPendingFactory2, which is supposed to be more
general than ExPendingCommandFactory (and similar interfaces), and
planned to replace these interfaces.
ExPendingFactory2 is to be used for syncing commands when propogations
have finished, such that it is ensured that a progogation is finished
before doing something. Further, the executed command and its result are
passed to this syncing method (afterPropogationFinished).