Store raw TAP output rather than the aggregator

The aggregator object does not capture the full output of the tests,
merely the ok/nok status of each line.  For a complete view of what
occurred in the test, instead capture and pass on the raw TAP output.
Merge STDERR into the raw tap

This requires the diag-merge branch of https://github.com/alexmv/Test-Harness.git
Merge branch 'full-tap'