Feature: Literal duplication - two times the same replacement in the same rule

[MaxOstrowski]

Especially inside conditionals it was hard to track where to do the replacement, as the rule is already overwritten in the first step.
Maybe accumulate all RuleRebuilders for this one replacement set and replace them all at once for this rule.

xysubgrid(X1,Y1,X2,Y2) :- xrow(X1); ycolumn(Y1);
                          xrow(X2); ycolumn(Y2);
                          ((X1-1)/3) = ((X2-1)/3);
                          ((Y1-1)/3) = ((Y2-1)/3).

[MaxOstrowski]

benchmarks/roomplanning/MNF-Roomplanning.asp

#false :- book(Course1,ID1); preference_room(ID1,Room); preference_day(ID1,Day); preference_time(ID1,Time); 
          book(Course2,ID2); preference_room(ID2,Room); preference_day(ID2,Day); preference_time(ID2,Time);
          not simultaneous(Course1,Course2); Course1 < Course2.

gets translated to a mess.