Add copy and revert commands to dockerctl

Revert: resets to latest image for container
Copy: copy files in and out of container
  Syntax:
    dockerctl copy src dest
    Only one of src or dest may be a container path
  New function examples:
    dockerctl copy /root/newpkg.rpm nailgun:/root/
    dockerctl copy nailgun:/etc/nailgun/settings.yaml /root/

Change-Id: Ia3cc999f6dc706b83d840a0e54c976c1bde2b6d4
Merge "Add copy and revert commands to dockerctl"