Brainstem should support options to refresh/clear request parameters

[naganowl]

There are use cases where we are making requests (usually filters) where the parameters are additive and it be nice to have Brainstem add the params to the last fetch options automatically (via a deep merge). We might be able to leverage the existing refresh call and/or make that an option.

On the flip side, we also want the ability to blow away all the parameters (except the ones specified) in case we are performing a reset/clear of the request.

For backwards compatibility, this could just be a refresh to trigger between making incoming options additive vs. replacement.

[juanca]

What about options similarly named to backbone options, e.g. add, remove, reset type of deal?

[naganowl]

Probably could use reset: true for flushing the options and reset: false for adding them on.