* Slightly tighten some self-check conditions
* Redefined the database descriptor object as reference (to the object)
why:
The upcoming transaction wrapper will work with a database reference
rather than the object itself
* Append state before `save()` to the Aristo descriptor
why:
This stae was previously returned by the function. Appending it to
a field of the Aristo descriptor seems easier to handle.
* Fix missing branch checks in transcoder
why:
Symmetry problem. `Blobify()` allowed for encoding degenerate branch
vertices while `Deblobify()` rejected decoding wrongly encoded data.
* Update memory backend so that it rejects storing bogus vertices.
why:
Error behaviour made similar to the rocks DB backend.
* Make sure that leaf vertex IDs are not repurposed
why:
This makes it easier to record leaf node changes
* Update error return code for next()/right() traversal
why:
Returning offending vertex ID (besides error code) helps debugging
* Update Merkle hasher for deleted nodes
why:
Not implemented, yet
also:
Provide cache & backend consistency check functions. This was
partly re-implemented from `hashifyCheck()`
* Simplify some unit tests
* Fix delete function
why:
Was conceptually wrong
Jordan Hrycaj