Reorganized artifact-related classes

- files now generally contain only 1 class (except for tightly coupled
classes)
- files are now located in lib/entities/artifact directory
- removed excessive includes

No changes to functionality

lib/bonuses/Limiters.cpp

@@ -21,7 +21,6 @@
 #include "../texts/CGeneralTextHandler.h"
 #include "../CSkillHandler.h"
 #include "../CStack.h"
-#include "../CArtHandler.h"
 #include "../TerrainHandler.h"
 #include "../constants/StringConstants.h"
 #include "../battle/BattleInfo.h"