Support for configurable town fortifications

Removed most of hardcoded checks for fort level or for presence of fort/
citadel/castle buildings.

It is now possible to define which parts of town fortifications are
provided by town buildings

Configuration for H3-like fortifications is provided in
buildingsLibrary.json and will be used automatically by mods as long as
mods have buidings named "fort", "citadel" and "castle".

Alternatively, mods can separately define:
- hitpoints of walls (shared value for all sections)
- hitpoints of central, upper and lower towers (separate values)
- presence of moat
- shooters for each tower (separate values)

server/battles/BattleProcessor.cpp

@@ -23,6 +23,7 @@
 #include "../../lib/battle/CBattleInfoCallback.h"
 #include "../../lib/battle/CObstacleInstance.h"
 #include "../../lib/battle/BattleInfo.h"
+#include "../../lib/entities/building/TownFortifications.h"
 #include "../../lib/gameState/CGameState.h"
 #include "../../lib/mapping/CMap.h"
 #include "../../lib/mapObjects/CGHeroInstance.h"
@@ -192,7 +193,7 @@ BattleID BattleProcessor::setupBattle(int3 tile, BattleSideArray<const CArmedIns
 bool BattleProcessor::checkBattleStateChanges(const CBattleInfoCallback & battle)
 {
 	//check if drawbridge state need to be changes
-	if (battle.battleGetSiegeLevel() > 0)
+	if (battle.battleGetFortifications().wallsHealth > 0)
 		updateGateState(battle);
 
 	if (resultProcessor->battleIsEnding(battle))