docker instructions: no docker directory

[riebling]

the instructions in doc/docker.md mention needing to navigate to a docker directory, but I think the Docker stuff is now actually in the top level directory
Also the suggested URL to git clone the code mentions 'ging' which was confusing at first until realizing that it resolves to 'lynckia'.

[riebling]

Another improvement: in a couple places I notice documentation that uses XX.XX.XX.XX in place of an IP address. People may think they need to literally type this, but it's probably meant to be a placeholder for an ACTUAL IP address; this should probably be explained or at least mentioned ("replace the 'X'es with your own desired IP address"). Not everyone will know this is expected/assumed.