OM NOM NOM! The hero can eat/take(whatever) mana crystals. 
HeroObject.h/cpp: created array which store amount of energy of every type. Also, function to get data from it and to use mana crystal 
GameLogic.h/cpp: replaced vector by list. Now it check collisions between hero and crystals and if they occur it remove crystal and call a special function for hero 
GameObject.h/GameItem.h: isItemObject function was added
Game.cpp: changed because GameLogic uses list instead of vector.