Savable state in `Controls`

If the user calls `useState` in their website and passes the `state` and `setState` values to the component they will be able to keep track of the `controls` state. This way they'll have control over whether or not loading a new dataset changes all of the controls

Would have to document how `setState` is called within the library much better.

Would make #17 easier much easier. Perhaps should do both in the same PR? Then document why you would use them separately (savable state)