Read_conversion variable save to json

[MTI-GMays]

Is your feature request related to a problem? Please describe.
unable to output read conversion's passed function variable to json

Describe the solution you'd like
Add another variable like args_passed as a read attribute in conversion.rb to just a save the variable passed in to the function to json.

[jmthomas]

It looks like accessor.rb is storing the args similar to this suggestion. Add @args to conversion, edit packet_item and packet_item_spec.rb::self.from_hash to ensure conversions can "round trip". May also have to modify packet_config.

Ensure changes across both Ruby and Python.