Add tests to verify basic function with supported VNC servers

[consideRatio]

We have no tests setup, and we have seen how changes we make have broken things either for users of TigerVNC or users of TurboVNC. With this in mind, I'd like us to ensure that we can at least startup things successfully without erroring when using all of the VNC servers we decide to support.

• TigerVNC
  Tested here to start successfully, which is possible because its installed in our Docker image.
• TurboVNC
  Not tested yet!

I think a way to help us test TurboVNC also is to go for #88 and provide a TurboVNC image as well.