Added result summary to json test results

* Changed the structure of the JSON result to include
  a result summary. This provides partity with XML
  results and allows metric calculations on JSON results
  without the need to caculate failures/errors/skips
  for each result set

Change-Id: Ia8f0a4a90d7d29e834a0e807377996a0aa87ec61
Merge "Added result summary to json test results"