Consider Function Signature conversions

From a [review of PR #2](https://github.com/AllenNeuralDynamics/one-liner/pull/41), @micahwoodard mentioned it could be useful to be able to change function parameter names, i.e: to be able to change the name of a kwarg from one value to another.

Generally, we might be able to achieve this from a lambda function written on the server side and then passed in instead of the original function, but let's consider what the api would be for doing this internally to see if it's worth it. The benefit of supporting it in the function call is that we could drive the entire `RouterServer` setup from a config instead of from code.