GUI: removed cross-site scripting hack

- Removed cross-site scripting solution for development purposes.
  From now on, we expect, that GUI and RPC runs on same server and port.
- This change removes 30sec timeout restriction. GET calls can now
  last up to 5 minutes (Apache timeout).
- This change also allows us to properly handle 401,404,500,503 cases, where
  404 and 503 are returned during RPC redeploy, 401 on wrong authz and
  500 on timeout or server internal error.
- This change prevent us from simply pointing RPC url in GUI config to devel
  or production. We must run local webserver and RPC. Issue is covered on
  our internal wiki.