* remove unused code
* reorg code to make the access to disk be outside the mutex
* add detection of slow disk-writes and slow down data coming in
* Update and fix the rmHint
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