Rename Name method of Repository to Named

This makes code that gets the name as a string read like
repo.Named().Name() instead of repo.Name().Name().

Requested in
https://github.com/docker/docker/pull/19887#discussion_r51479753

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

docs/storage/blobwriter.go

@@ -326,7 +326,7 @@ func (bw *blobWriter) moveBlob(ctx context.Context, desc distribution.Descriptor
 // resources are already not present, no error will be returned.
 func (bw *blobWriter) removeResources(ctx context.Context) error {
 	dataPath, err := pathFor(uploadDataPathSpec{
-		name: bw.blobStore.repository.Name().Name(),
+		name: bw.blobStore.repository.Named().Name(),
 		id:   bw.id,
 	})