Add option to status watch command to give JSON output

[lossyrob]

The command which currently polls for workflow status is pctasks records status workflow --watch ${WORKFLOW_ID}. This provides useful console output for users to see how their workflow is progressing. However, it would also be useful for any automated systems that submit a workflow and want to wait until the job succeeds or fails. In that case, it would be ideal to have some JSON output to stdout that gives job information, like whether it passed or failed, so that one could script downstream processing based on the result of the workflow.

E.g. something like pctasks records status workflow --watch --json ${WORKFLOW_ID}