TDML Runner must provide root namespace to processor

Daffodil's TDML processor can determine the root element namespace URI by searching.

Other TDML processors can't do that.

This turns out to make it impossible to run TDML negative parser test cases, because there is no infoset from which the namespace can be determined. So, for example on the IBM Cross Tester's TDML Processor, a parserTestCase that is negative always fails with 'can't find root element' whenever there is a target namespace in the schema.

1) add a way to specify the root namespace URI on a test case (e.g., rootNS attribute)

2) add a heuristic to grab targetNamespace of primary schema file or schema node

Pass this namespace string so that it is supplied to the processor.