Release Pipeline should have version parameter

[eriksven]

We need a pipeline in the Jenkins Server at the Eclipse Foundation to upload a new release archive to the download server of the Eclipse Foundation. This is described in /releng/ReleaseJenkinsfile. As of now the version is hardcoded in that file. To make future releases easier the file should accept the version as an argument and use it accordingly (e.g. by checking out the corresponding tag and setting the name of the release archive).