mv references from read*.avdl to reference*.avdl

Just a move. No change in schema content. This seems like an inevitable change, as other GA4GH models would hopefully eventually refer to `GAReferenceSet`s as well, e.g. `GAVariantSet`.

Also update pom.xml so that I can run `mvn test -B` locally.
Fixed... Apparently my emacs is not well equipped for XML and added some secret tabs here.