Create the Filtering Class

[vforgione]

Requests to the API should be able to have filters applied. JS doesn't offer some of the nice shortcuts we get in Python, but that doesn't mean we can't build out some cool things here.

We need a filter class, maybe F is still a good enough name. That class can be initialized with either nothing or a tuple for the first filter.

We also need to build out the ability to add filters, join filters on key (as a result of adding a filter with the same name), and replace filters.

• constructor
• addParam (look at the Python &= overload)
• overrideParam (look at the Python |= overload)