Implemented the docker-login common role

configures Docker CE with credentials for private a repository.

roles/docker-login/defaults/main.yml

+---
+# A list of docker credentials. For example:
+# docker_login_registry_credentials:
+#   friendly_name:
+#     username: example
+#     password: some-pass
+#     registry: https://repository.invalid/
+docker_login_registry_credentials: {}