Move registry package out of repo root

Since the repo is no longer just the registry, we are moving the registry web
application package out of the repo root into a sub-package. We may break down
the registry package further to separate webapp components and bring the client
package under it. This change accomplishes the task of freeing up the repo root
for a distribution-oriented package. A stub doc.go file is left in place to
declare intent.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

cmd/registry/main.go

@@ -12,10 +12,10 @@ import (
 	"github.com/gorilla/handlers"
 	"github.com/yvasiyarov/gorelic"
 
-	"github.com/docker/distribution"
 	_ "github.com/docker/distribution/auth/silly"
 	_ "github.com/docker/distribution/auth/token"
 	"github.com/docker/distribution/configuration"
+	"github.com/docker/distribution/registry"
 	_ "github.com/docker/distribution/storagedriver/filesystem"
 	_ "github.com/docker/distribution/storagedriver/inmemory"
 )