effective error handling when filesystem is modified

[breezykermo]

Because mtriage uses the local filesystem to store state/data between passes, there is always the possibility that it will be corrupted between selects/analyses.

Mtriage doesn't currently have much in the way of effective error handling when the file system is corrupted, but should do its best to alert the user what the problem is.

[breezykermo]

This still isn't exactly solved, but making storage abstract has helped towards this. That API could probably be refined to do better with errors.