update applyDigestToBlobs to return a FixityResult object with the checksum and size
fix up stuff
take another stab at .getFixity; let the consumer decide what to do with the fixity information.
Merge branch 'master' of https://github.com/futures/fcrepo4
fix up FedoraDatastreams to use new getFixity method
Merge branch 'master' of https://github.com/futures/fcrepo4