Have multiple lists of MC files in the campaigns config

Release Notes

Read multiple data and MC file lists in the campaigns config, either with the dataFileList and mcFileList options or their plural forms.

Details

This adds the options dataFileLists and mcFileLists to the campaigns config file, which, as the name suggests, allows to give multiple text files with paths to the MC samples. dataFileList and mcFileList were changed to the same behaviour.

Usage example:

[mc16e]
dataFileList: config/samples/inputFileLists/ssWW/ssWW_data18FileList_DESY.txt
dataFileListTreeName: CollectionTree
mcFileLists: config/samples/inputFileLists/ssWW/ssWW_mc16eFileList_DESY.txt, config/samples/inputFileLists/ssWW/0nubbtest
mcFileListTreeName: CollectionTree

Thanks to @cburgard for explaining how to approach this.

Also, ignore the CI pipeline warning. The pipeline for master also doesn't work on my fork. But somebody with access to a working pipeline should probably check.