Implemented configuration frame work

Added reading and writing machinery's configuration file.
The file machinery_config.rb contains the default values
used when no configuration file is present.

The method name `get_human_readable` doesn't result in very readable code, as it doesn't contain an object, so when reading the code the parameter reads like the object. But this is not what the method is doing. It doesn't turn the string "string" into a human-readable thing, but returns the value of the config entry "string" in a human readable format. Maybe `subject.get("string").as_human_readable` would be nicer. (This would imply representing config entries as objects, see my general comment on the pull request).