Improvements for json validation for mods

- Implemented validation for `targetCondition` in spells
- Implemented validation for `mapObject` in towns/heroes
- Fixed validation of zone connections in RMG
- Added workarounds to prevent assertions triggering on invalid mods
- Erase 'base' entries from json before validation (but after applying
them to derived keys)

Should have no effect on mod behavior/support, but may cause new
detections for mods that were broken in either 1.6 or 1.7

lib/json/JsonBonus.cpp

@@ -536,14 +536,16 @@ static std::shared_ptr<const ILimiter> parseCreatureTypeLimiter(const JsonNode &
 		creatureLimiter->setCreature(CreatureID(creature));
 	});
 
-	creatureLimiter->includeUpgrades = upgradesNode.Bool();
-
 	if (upgradesNode.isString())
 	{
 		logGlobal->warn("CREATURE_TYPE_LIMITER: parameter 'includeUpgrades' is invalid! expected boolean, but string '%s' found!", upgradesNode.String());
 		if (upgradesNode.String() == "true") // MOD COMPATIBILITY - broken mod, compensating
 			creatureLimiter->includeUpgrades = true;
 	}
+	else
+	{
+		creatureLimiter->includeUpgrades = upgradesNode.Bool();
+	}
 
 	return creatureLimiter;
 }