* Generalised Aristo DB constructor for any type of backend
details:
* Records to be deleted are represented as key-void (rather than
key-value) pairs by the put-function arguments
* Allow direct driver access, iterators as example implementation and
for testing.
* Provide backend storage interface
details:
Stores the top layer onto backend tables
* Implemented Rocks DB backend
details:
Transaction based `put()` functionality
Iterators (based on direct RocksDB access)
4b66f93274