Add signing and verification code for blob permissions
Code review for 1844-blob-signature: documentation, slight refactoring (refs #1844)
Merge branch 'master' into 1844-blob-signature
Merge branch '1844-blob-signature'
Fix CollectionReader treating any collection with additional +hints as
an empty manifest.

Now, accept hash+size+anyhints as a UUID, and if the argument looks
like neither a UUID nor a manifest, raise an exception instead of
proceeding with undefined results.