Add some basic handling to set cross-origin resource sharing headers for
the satellite UI app handler as well as API endpoints used by the
satellite UI.
This change also removes some no-longer-necessary CORS functionality on
the account registration endpoint. Previously, these CORS headers were
used to enable account registration cross-origin from www.storj.io.
However, we have since removed the ability to sign up via www.storj.io.
With these changes, browsers will prevent any requests to the affected
endpoints, unless the browser is making the request from the same host
as the satellite.
see https://github.com/storj/storj-private/issues/242
Change-Id: Ifd98be4a142a2e61e26392d97242d911e051fe8a
7530a3a83d