From now on, make sure that the minor always has at least 2 digits
which allows us to use string compare of versions even if we have
more than 9 releases in a year.
The "UAHF" one used to be "more equal", mostly just because it happened
to be the first.
This makes them all equally equal.
Specifically this removes the special casing and the enum for the 201708
HF (aka BCH fork-point).
We select the right branch now purely based on the historical check-
points.
During the BCH fork-off time we allowed the client to be started
as either BCH or BTC and as such there are several code-paths
that behave different based on this user setting.
We remove those as we no longer allow starting as BTC client.
This also removes the check for the min-block-size (rollback protection)
as this is accomplished by the checkpoints on the BCH chain.
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.
Remove no longer useful options;
* chain (sorry, supporting the btc chain just doesn't seem worth it)
* initiatecashconnections, we only allow Cash connections now.
* flexiblehandshake, same for incoming. Reject non-cash ones.
TomZ