Explained co-ordinate system

How to refer to cubes in a human-understandable way, and how to give
them a unique ID internally so they don’’t get out of synch in the game
logic.
Fixing comments

Changed comments to say ‘headers’ instead of ‘includes’ to match
everywhere.
Preparing common code expansions

Added placeholder files for an error logger class and a string utility
class for things like quoting and unquoting terms, and token parsing.