* The example_xx.xml files are the official PROV-XML examples from the
  specification. Examples 4 and 5 are tested separately in the XML test case.
  Some files had to be adjusted a bit to be valid according to the spec.
* prov_primer_complete_example.xml: This is the complete example from the
  PROV Primer documentation. It had to be adjusted a bit to be valid
  according to the spec.
* pc1.xml: Provenanve Challenge 1 like file from
  https://github.com/lucmoreau/ProvToolbox/blob/master/prov-xml/src/test/resources/pc1.xml
  Had to change a couple of minor ordering/formatting issues to be able to
  do the round trip.