passing non-stringified objects in runner

[madhur-ob]

This allows us to use the Runner API as follows:

Earlier:

Parameter('targets', type=JSONType, default={'abcd': 123})
with Runner("jj.py").run(anchor_date=anchor_date_str, targets='{"US": 1}') as running:

^^notice how passing a string version of json in the runner API

Now:

Parameter('targets', type=JSONType, default={'abcd': 123})
with Runner("jj.py").run(anchor_date=anchor_date_str, targets={"US": 1}) as running:

^^notice how passing the json directly in the runner API