Serve spartacus on -dev

* This adds the views to serve spartacus.
* I've split the settings to ENABLE_SPA_URLS and ENABLE_SPA so we can handle the urls with less pain in the tests. The urls that are enabled in the ENABLE_SPA_URLS setting are different to the core webpay urls this means we can handle testing both the API and the basic views because these are enabled for tests.