Small refactor; move the partition check away from main and the obsolete
global variables we used to use, instead now just add it to the DB which
owns the data it works on.
This fixes the bug that in various cases we'd incorrectly get a warning
about no blocks being found in the last N hours.
To allow the UTXO to actually use the power of checkpoints we need to
make sure that the block-validation state is not stored separately from
it.
The goal is that when we have some curruption we can just go back to an
earlier state of the UTXO and re-validate the blocks to get to the
current tip. The often seen problem is that corruption will instead
leave the block-index (leveldb) with an incorrect state so the replay
fails.
This change solves that by no longer reading the block-validation-state
and no longer writing it on a state change.
Instead of having a magic 10 open files, we now have a scheduled
run that closes all mapped files 30 seconds after last usage.
This allows many files to be opened with extremely low overhead and
cost (they are not actually loaded until needed, and even then only
per 4K page).
The new UnspentOutputDatabase classes are only very loosly a database, we
purely register and store unspent outputs there. But unline a DB we don't
allow modification (just insert and delete).
This replaces the coin-db (which was based on leveldb) and as first goal
this gives us a higher level of stability. The level-database was known
to give corruption issues.
Notice that users will need to do a manual reindex on first update.
TomZ