Added wfdesc example of Nebojsa's Rabix workflow

See https://groups.google.com/d/msg/common-workflow-language/oIWTGq3rHcw/9d0q0FjJqMQJ

    <examples/bwa-and-freebayes-workflow-wfdesc.json>
         pav:derivedFrom <https://groups.google.com/d/msg/common-workflow-language/oIWTGq3rHcw/9d0q0FjJqMQJ> .