add "colorless" manacost

The symbol {C} will be used going forward to represent one colorless
mana. The numerical and variable mana symbols ({1}, {2}, and so on,
including {X}) will still be used, but only to represent costs that can
be paid with any type of mana.

example card: To cast Spatial Contortion, you pay two mana: one generic
(that's the {1}) and one colorless (that's the {C}). The generic mana
cost can be paid with any type of mana—that means any color or
colorless. But the {C} is different. That can be paid only with
colorless mana.

projects/mtg/src/ManaCost.cpp

@@ -79,6 +79,11 @@ ManaCost * ManaCost::parseManaCost(string s, ManaCost * _manaCost, MTGCardInstan
                 {
                     manaCost->add(Constants::MTG_COLOR_RED, 1);
 
+                }
+                else if (value == "c")
+                {
+                    manaCost->add(Constants::MTG_COLOR_LAND, 1);
+
                 }
                 else
                 {