GitLab

CI improvements

See merge request !3

Runner now creates test tags for non-master branches.  For the master
branch, the image is assigned the "latest" tag.

CI with Docker build

See merge request !1

* Removed unnecessary packages
* NPDet updated
* DD4hep customized until we can get a PR through for preventing CMake "install" by DD4hep cmake functions

Also...
* Added GenFit to /opt for now
* Added env variables that LCIO wants when loaded in cling

Since the PRs required to make DD4hep behave nicely in this image have been
merged, we can go back to the offical repo.

This variable is currently not needed

to the top of the ROOT section.