Changes:
* Add apt-release.sh and repository-release.sh, two scripts
  based on the aux ones used by python-release now but able
  to handle generic repository names.
* The repository-release.sh is able to clone the git repo
  from gerrit if not present on the build node.
* Add specific actions to scp the above files to the right hosts.
* Add a warning about checking the status of the repo directory
  on the build node.

Manually tested (not with a complete release though).

Bug: T367410