Setup a CI in gitlab.cern.ch to create a docker image of the framework

[lenzip]

Setup a CI so that an image of mkShapesRDF is built upon commit/merge of a MR. Setup it in such a way that the image is also uploaded on /cvmfs/unpacked.cern.ch, so that it can be used in HT_Condor jobs by adding to the jds file a line of the kind:

+SingularityImage = "/path/to/your/image/in/cvmfs/"

This removes the need to have a shared filesystem between the worker nodes and the submission node.

[lenzip]

Work in progress in my fork: https://gitlab.cern.ch/lenzip/mkShapesRDF/-/tree/ci_kaniko?ref_type=heads