Transition to v4 of the api

The v4 version of the api, when finished, will require that various pieces that are served up by vpnweb, be available on the /4/ endpoint, instead of on /3/. Right now, everything is coded as /3/, and maybe we should keep 3 around for a bit, while people transition, but add in a /4/ endpoint so we can start building out the new features that we want to have in that api version.