Using a separate ssb-server for testing

@RavteCyber

Export environmental variable ssb_appname=ssb-test. That makes ssb-server and ssb-client use ~/.ssb-test instead of ~/.ssb, including automatically making a new secret file in ~/.ssb-test if needed. Then don't follow anyone or use invites from the main network from the test id, or vice versa.
To run it alongside normal ssb, make it use different ports. Put in ~/.ssb-test/config:

{
  "port": 8007,
  "ws": {
    "port": 8988
  }
}

For good measure, set sign and shs caps, as mentioned by @aig in %y00L8pC... and by me in thread %tQakYap..., also referencing @josiah's guide %tWGy2kn.... e.g.:

{
  "port": 8007,
  "ws": {
    "port": 8988
  },
  "caps": {
    "shs": "o9dkRr3BsTYxRJ1dLDXlk0FjPZ0LsP6Tti8PlYUEMU0=",
    "sign": "K84etuJU/BQ5R8eYb0U0I4pUVZfyEcLVlIiKxDg1RAE="
  }
}