Add recipe file

recipe.yaml

+version: 1
+user: smosciat
+cvmfs_repo: 'unpacked.cern.ch'
+output_format: 'https://gitlab-registry.cern.ch/unpacked/sync/$(image)'
+input:
+    - 'https://registry.hub.docker.com/library/fedora:latest'
+    - 'https://registry.hub.docker.com/library/debian:stable'
+    - 'https://registry.hub.docker.com/library/centos:latest'
+    - 'https://registry.hub.docker.com/library/centos:centos6'
+    - 'https://registry.hub.docker.com/library/centos:centos7'