General fixes - Code quality, Configurable Config Directory, Update Docker

[bertybuttface]

This is a tidier version of my previous pull request but rebased upon your latest commit and without the hacks I had to make to get this to work with a Home Assistant Addon. Once I've found a cleaner way to do it instead of hacking it I will put a second PR in.

[mmcc-xx]

looks good to me - I'll merge this later today when I have time to do some quick tests.