OUT/RulesParser: update todo

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
OUT/RulesParser: IfProduction

Make an IfProduction a list of IfClauseProductions, and implement
IfClauseProduction, and subclasses ElseClauseProduction and
ElifClauseProduction to represent the supported clause types.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>