Implement city production projects for units and buildings

unitconfig.h

@@ -39,6 +39,7 @@ struct UnitConfig {
     int health;
     float movementSpeed;
     int cost;
+    int laborCost;
     int attackDamage;
     int attackRange; // 1 for melee, >1 for ranged
     int buildCharges;
@@ -52,7 +53,7 @@ struct UnitConfig {
     UnitConfig()
         : id(""), name(""), category(UnitCategory::Builder),
           movementDomain(MovementDomain::Land), health(100),
-          movementSpeed(2.0f), cost(10), attackDamage(0), attackRange(1),
+          movementSpeed(2.0f), cost(10), laborCost(1000), attackDamage(0), attackRange(1),
           buildCharges(-1), infiniteCharges(true), iconPath("") {}
 
     bool isRanged() const { return attackRange > 1; }