Truth matching for merged particle containers

Allow truth-matching of ParticleContainersMerger with custom relations tables in MCTruthAndBkgCat.

Example in this test

Also allow for truth_match_candidates and truth_match_lines to be called multiple times in the same job. Note: this will change the output location of the relations tables to a non-default location. The persistency expects the relations-tables to be in the default location, but when running e.g. a tupling job the location of the relations-tables does not matter.