Made draggable skill icon so that when dragged to the enemy, the action skill will be performed.
Refactoring to add screenPosition field to EnemyAttributes.
Merge remote-tracking branch 'origin/master'

Conflicts:
	Classes/Communication/Handlers/AnimationLetterHandler.m
	Classes/Communication/Handlers/SoundLetterHandler.m
	Classes/Communication/LetterType.h
	Classes/GameLogic/Battle/Skills/CharacterSkill.m