Change from CCUpgrade to pure sc2::UPGRADE_ID

CCUpgrade (sc2::UPGRADE_ID) does not contribute much and makes code
more difficult. Especially in Python, since it does not convert between
types implicitly.

src/TechTree.h

@@ -24,7 +24,7 @@ struct TypeData
     sc2::AbilityID          warpAbility     = 0;            // the ability that creates this item via warp-in
     std::vector<UnitType>   whatBuilds;                     // any of these units can build the item
     std::vector<UnitType>   requiredUnits;                  // owning ONE of these is required to make
-    std::vector<CCUpgrade>  requiredUpgrades;               // having ALL of these is required to make
+    std::vector<sc2::UPGRADE_ID>  requiredUpgrades;         // having ALL of these is required to make
     std::vector<UnitType>   requiredAddons;                 // a unit of this type must be present next to the producer
 };