Upstream conformance tests are being updated, so we need to align along
with our internal GC and dedupe features.
Add a new example config file which plays nice with conformance tests.
DeleteImageManifest() updated to deal with the case where the same
manifest can be created with multiple tags and deleted with the same
digest - so all entries must be deleted.
DeleteBlob() delete the digest key (bucket) when last reference is
dropped
As the number of repos and layers increases, the greater the probability
that layers are duplicated. We dedupe using hard links when content is
the same. This is intended to be purely a storage layer optimization.
Access control when available is orthogonal this optimization.
Add a durable cache to help speed up layer lookups.
Update README.
Add more unit tests.
