* Remove `dirty` set from structural objects
why:
Not used anymore, the tree is dirty by default.
* Rename `aristo_hashify` -> `aristo_compute`
* Remove cruft, update comments, cosmetics, etc.
* Simplify `SavedState` object
why:
The key chaining have become obsolete after extra lazy hashing. There
is some available space for a state hash to be maintained in future.
details:
Accept the legacy `SavedState` object serialisation format for a
while (which will be overwritten by new format.)
* Remove all journal related stuff
* Refactor function names journal*() => delta*(), filter*() => delta*()
* remove `trg` fileld from `FilterRef`
why:
Same as `kMap[$1]`
* Re-type FilterRef.src as `HashKey`
why:
So it is directly comparable to `kMap[$1]`
* Moved `vGen[]` field from `LayerFinalRef` to `LayerDeltaRef`
why:
Then a separate `FilterRef` type is not needed, anymore
* Rename `roFilter` field in `AristoDbRef` => `balancer`
why:
New name more appropriate.
* Replace `FilterRef` by `LayerDeltaRef` type
why:
This allows to avoid copying into the `balancer` (see next patch set)
most of the time. Typically, only one instance is running on the backend
and the `balancer` is only used as a stage before saving data.
* Refactor way how to store data persistently
why:
Avoid useless copy when staging `top` layer for persistently saving to
backend.
* Fix copyright header?