Expose Nuxeo build and release version for downstream jobs

From the build and release pipelines of Nuxeo and Nuxeo JSF UI, make it possible for downstream jobs to get the build and release version of Nuxeo and/or Nuxeo JSF UI.

The upstream jobs can be retrieved through:

for (RunWrapper build : currentBuild.upstreamBuilds) {
// do something
}

Each build is a RunWrapper, and the RunWrapper#getBuildVariables could be used to get back build variables from the upstream job.