Add React Router for page navigation

[sleepycat]

Ultimately we'd like to help people explore these controls, and send people links to controls and their descriptions. That means we'll need proper URIs for these things and that means using React Router.

We'll need to create a slugified version of these control ids (something like /ac-2-2) to support this deep linking, which we'd need to expose the slugs via the api (as a field on the Control type and as something we can use to retrieve controls with).

[samiatoui]

Partially completed. React Router has been setup. Back-end work needs to happen to generate the slugs.