Merge vault.blob and vault.store namespaces.
Rename blob/hash-content to blob/digest.
Refer to blobrefs as identifiers not addresses.

An 'address' implies a location, such as in a URL, whereas blobrefs are
URNs, so the more general 'identifier' from URI is more appropriate.
Factor out printing code into 'puget' library.
Rename ns vault.tool.command to mvxcvi.cli.

This should eventually be factored into its own library.
Merge branch 'refactor-ns' into develop