A clock that tracks the current sequence number and the version vector of an event log.
The version vector is the merge result of vector timestamps of all events that have been
written to that event log.
Sets sequenceNr to max of sequenceNr and processIds entry in versionVector.
Advances sequenceNr by given delta.
Sets sequenceNr to the event's local sequence number and merges versionVector with
the event's vector timestamp.