-new supported launch.json settings
-feature: multi-user debugging,
-troubleshooting: run your own local proxy

- allowMultipleSessions, enable, host, key, port

- Implementation of ProxyConnect class.
- Upon initialization, will request registration with the proxy
- new launch options
  - allowMultipleSessions, enable, host, key, port

- in addition, add `Non-null assertion operator` where appropriate

- these aren't going to, nor should they, change while tests are running

- has no affect on render
- easier viewability when editing the raw document collapsed

- abstract out what the full php version is
- update hardcoded full php version in appveyor
- update base macos image

…ivate

- new ProxyMessage interface to ensure typesafe messages
- socket is now private and can be passed through constructor

…andom port and register that with the proxy.