Remapping of port 8080 in docker setup

[MartinKirchner]

@ryansch Thanks for your work in this project.

I had some trouble with the network controller showing the devices Offline or in Adopting state. To fix the Offline issue it was necessary to additionaly expose the port 10001, the cause for the Adopting state was that I remapped the port 8080 to 8081. To fix this I had to connect to my devices using SSH and tell them the controller's URI.

I forked your repo and documented my solution in the likewise cloned wiki (unfortunately github does not seem to allow pull requests for wikis).

My wiki: https://github.com/MartinKirchner/docker-unifi-rpi/wiki#remapping-of-port-8080

Maybe you want to add this to your documentation.

Best regards, Martin