Finally shattered CObjectHandler.cpp into tiny bits

- This file is now split into multiple smaller files in mapObjects
directory
- CObjectHandler itself now contains only core classes (Handler itself,
CGObject and interfaces)
- Cleaned up excessive #include's through whole project

lib/CArtHandler.cpp

@@ -16,11 +16,13 @@
 #include "VCMI_Lib.h"
 #include "CModHandler.h"
 #include "CSpellHandler.h"
-#include "mapObjects/CObjectHandler.h"
+#include "mapObjects/MapObjects.h"
 #include "NetPacksBase.h"
 #include "GameConstants.h"
 #include "CRandomGenerator.h"
 
+#include "mapObjects/CObjectClassesHandler.h"
+
 using namespace boost::assign;
 
 // Note: list must match entries in ArtTraits.txt