Namespaced parameters syntax improvement

[MSeal]

Passing objects representing dicts is painful in papermill right now. You have to pass each value individually and catch the corresponding names inside the notebook. But when you have a large group of parameters all together (in say a json object) it'd be very convenient to specify those associated values on the input side but not inside the notebook.

Specifically a syntax along the lines of -p foo.bar.baz value could be passed to the command line resulting in the parameters cell a dict of form "foo" = {"bar": {"baz": "value"}}}. For repeated paths the dict could be enriched such that a second param of the form -p foo.bar.baz2 value2 would combine to form foo = {"bar": {"baz": "value", "baz2": "value2"}}}. These parameters wouldn't need to share prefix paths, so -p foo.bar2 baz3 would augment the top foo dict instead of the nested foo -> baz dict.

This would enable passing dynamic or many valued parameters that are together associated as individual inputs which are human readable and getting a clean hierarchy of dicts on the output.

Given the merge behavior of each assignment it could also be used to merge with existing dict variables to provide foo = {'default': 'values'} beforehand and have augmentation via the command line pass-through.