Add a minimal b-tagger example

I promised @cantel and @sfranche that I'd give them a minimal example that ran DIPS on jets. The code in getSimpleJetTagConfig is more or less what you need.

The ca-dump-minimal-btag script is really the most basic b-tagging we can do: associate tracks to jets, run DIPS on them. We don't even create a BTagging object. There's another example that creates a BTagging object, but that one only works if no object already exists: otherwise it breaks when it tries to overwrite btaggingLink.

I also added a unit test for this, but it doesn't go all the way to running in the CA job because of the issue above. I'll have to add a new file where jets aren't tagged, or make shallow copies of the jets, or maybe go the full distance and make btaggingLink configurable in the dumper, before the CI can run. That will come later.

I also tried to clean up the test-dumper script a bit.