Wrapper script for testing.
Ignore test output.
Show type instead of description for inputs and outputs.
Refactor: extract common code for extracting graphs.
Use Graphviz ranks to force Parameters to the top and Outputs to the bottom. This means that we can't use clusters because there is a bug in Graphviz that stops rank working for them; style Parameters and Outputs differently instead.
Cope with templates that don't have Parameters or Outputs.