Automated builds -- Allow to abort the build of a release:
  - The abort can be done when the status is build-in-progress,
    and no architecture is being uploaded or is already uploaded.
  - It removes the release in github and the tag in cmssw.
  - It removes the tags in cmsdist that could have been created.
  - After aborting, the new status of the issue is build-aborted.
    The user should create a new issue to start over.
Merge pull request #242 from nclopezo/allow-abort-builds

Automated builds -- Allow to abort the build of a release: