Remove outdated docker example

docker/Dockerfile

docker/pv_server.py

docker/pvlink/MANIFEST.in

docker/pvlink/README.md

docker/pvlink/RELEASE.md

docker/pvlink/js/README.md

docker/pvlink/js/lib/embed.js

docker/pvlink/js/lib/extension.js

docker/pvlink/js/lib/index.js

docker/pvlink/js/lib/labplugin.js

docker/pvlink/js/lib/remoterenderer.js

docker/pvlink/js/package.json

docker/pvlink/js/webpack.config.js

docker/pvlink/pvlink.json

docker/pvlink/pvlink/MANIFEST.in

docker/pvlink/pvlink/README.md

docker/pvlink/pvlink/RELEASE.md

docker/pvlink/pvlink/__init__.py

docker/pvlink/pvlink/_version.py

docker/pvlink/pvlink/js/README.md