Create inverse/negative test output

[ross-spencer]

This thread is interesting: digital-preservation/droid#805

If we reorganize the output we can create files, one per signature? That //shouldn't// match the DROID signature.

This does change the spirit of the suite a little, and right now I think the general use-case is "do all skeleton files match". Folks would be cherry-picking negative matches and would need enough context to say - this file //shouldn't// match signature X and sequence Y.