build the repairer

[warner]

It is time to build a Repairer service. This should accept a storage index, or a verifier cap, and:

• locate all existing shares
• read all existing shares, checking hashes, report bad ones
• generate+upload new shares as necessary

There should be a work queue, a directory of SI or verifier-cap (or repair-caps, once we define them). The files in the work queue directory should have one file per line, and the file will be deleted once all its files have been repaired.

Eventually we will make a foolscap inlet port for the work queue.

The Repairer service should be another twisted.application.service.MultiService?, like uploaders and downloaders and helpers.