Enable support for branching
This merge enables support for choosing alidist and jalien-root branch to test when creating a pipeline manually. The corresponding environment variables are: ALIDIST_BRANCH and JALIEN_ROOT_BRANCH. Both repositories come from gitlab.cern.ch/nhardi.
This merge also enables faster builds by targeting only JAliEn-ROOT instead of whole AliPhysics + AliRoot.
Edited by Nikola Hardi