Allow custom classes for Helper Components

I'm creating my own layout of a color picker input to use in our bootstrap site, however, using the `EditableInput` I can't reuse the styling already built into the bootstrap classes since there's no way to get them onto the elements.

I can build a style object to apply these styles but that's a lot of work to copy over all the styles that are already built into the bootstrap classes. If you're amenable I'd be happy to try and put together a POC pull request.

Ideally for something like `EditableInput` it would allow an object similar to the `styles` prop which would allow classes on each element inside (`wrap`, `label`, and `input`). That way I would be able to put `form-control` onto the input to keep consistent styling with our regular bootstrap inputs.

Start by locating the EditableInput component and reading how its styles prop is applied to the wrap, label, and input elements. Add support for supplying classes for those elements, then verify that a consumer can apply form-control to the input while retaining the existing styling behavior.

Written by the indexing model from the issue text.