Moved predefined substitutions into ParsedCommand
This means they are done on a command-by-command basis now instead of
all at the start, so substitutions in a chained command like "$x,1 &&
\\You now have <EXP> XP" actually report the right amount.  The previous
behaviour can still be obtained with e.g. "$x,1 \\You now have <EXP> XP"