MODE-1683 Simplified message consuming & receiving; updated delta reconciliation implementation and MapDB version to 0.9.8.
MODE-1683 Added a method for retrieving the last record of a journal. Changed the signature of the methods which used long timestamps to use DateTime(s) and removed unnecessary conversions to UTC.
MODE-1683 Changed from normal timestamps to time-based keys and updated various other parts of the code based on code review.