Path Based Routing Support

[paulotruta]

After lots of hours looking around, we discovered that unfortunately Windows does not support mDNS with subdomains. It just plainly refuses to acknowledge or even connect.

Path based routing seems the way to go. This would bring:

• Consistency between internet-accessible and internal-only urls (https://boxid.myedge.app/appid vs. http://edgebox/appid)
• Getting rid of the avahi dependency and ws domain publishing logic.
• For internal-network only apps, working in every device, no tricks needed.

This PR contains necessary code to test a custom build of nginx-proxy + docker-gen combo, based on these PR's:

• Lift restriction on the function contains nginx-proxy/docker-gen#343
• Support for path-based routing nginx-proxy/nginx-proxy#1594

CURRENT STATUS: Building but not working

[paulotruta]

Did a first test by building docker-gen from https://github.com/AlexanderLieret/docker-gen but bumped into some issues.
Will try again with fresh eyes some other time.