Version 1.3.0

- added Kerl as an additional hash function.
- Tips: improved memory consumption and IRI loading time.
- ZMQ:  tx topic only publishes newly stored transactions
        tx arrival time added.
        timestamps normalized to seconds.
- DB: cache size increase, to reduce flushes to disk (user-configurable)
- Node: faster broadcast priority queue
        DNS refresher is now user-configurable, for troubleshooting reverse-DNS issues.
- TipSelection: bugfixes & optimizations to MCMC.

• First snapshot as a part of 3-step phasing to the final design of transaction structure