Remote md5 and sha1 hashes which are not supported by distribution.
Add more secure hashes sha384 and sha512.
Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
The Digest type will be fairly central for blob and layer management. The type
presented in this package provides a number of core features that should enable
reliable use within the registry. This commit will be followed by others that
convert the storage layer and webapp to use this type as the primary layer/blob
CAS identifier.
