Handle kwargs passed to js functions

[YarnSaw]

Ticket to track thoughts on the conversation under #42 (comment).

Actual plan hasn't been decided yet.

[JosephAcernese]

To try to summarize:

• kwargs are currently ignored when passed to PythonMonkey, but could change in the future
• kwargs are used in various parts of Bifrost2, mainly to follow Python standard practices
• kwargs are not unwrapped if they're bifrost2 objects, but if they are ever used in the future, they will need to be

This leaves one main question, will Bifrost2 ever want users to pass keyword args to dcp-client?

• If the answer is no, kwargs should likely be removed from generic wrappers
  • This future-proofs it from any PythonMonkey changes to kwargs
  • kwargs passed to functions will TypeError, which is better for users than silently ignoring them
• If the answer is yes, kwargs will need to be unwrapped similarly to args