Fix retrieving the number of previous settlement-success transactions.
Implement marking transactions as SUCCESS, PRESETTLEMENTREJECT or POSTSETTLEMENTREJECT. Also add tests for rejecting transactions and creating files after that.
Fix directdebit ID generation: don't always include 0x00 at the end.
Eliminate chance of generating a duplicate authorization ID within the same process: while the PID is already used in the authorization code, a per-object counter is now also held so the same object only has a chance of generating a duplicate ID if at least 256 ID's are generated per second.
Implement directdebit file marking, including some tests.