CInbox may have issues if a signature exists twice in different states

[pjotrek-b]

There may be issues if the same signature is present more than once, in different state folders (todo, in_progress, error), at the same time.
There's also a known issue, if a logfile from previous runs is present - but in the wrong state-folder (eg not being moved back to todo, but left in error).

CInbox should check for that and handle/report it gracefully.