Move config files from config/ to config/example/

Moves all the game config files from config to an example subdirectory.
When people first clone the repo, they will need to copy files from
config/example into config, but this will only need to be done once
barring any `git clean` calls.
This allows developers to keep their admins.txt persistent, and allows
easy modification of the example files without having to reset.
README.md updated and .gitignore added for config.