Imports of package manifest

PathSynopsis
crypto/x509Package x509 implements a subset of the X.509 standard.
encoding/jsonPackage json implements encoding and decoding of JSON as defined in RFC 7159.
github.com/Sirupsen/logrus
github.com/docker/distribution/digest
github.com/docker/libtrustPackage libtrust provides an interface for managing authentication and authorization using public key cryptography.