The CAmount name is not helpful as its just an int64_t and not a
class, like the name implies. There were a handful of places where
it was passed in as const-ref, as a good example of this actually
creating sub-par code.
The RPC / HTTP servers were logging about being shutdown even if
they never were started in the first place. This confused people.
Also removed some empty methods.
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.