added accessor method getMap
added test save to datGui
convert map name to json
stub for conversion of Entities to json
added basic conversion of Entity to json
refactored parameters of Entity
simplified isClicked by delegating to isHovered
added dedicated methods for dealing with StateAnimations in Entity
added toJson method to AnimationSheet
added toJson method to Animation
added stateAnimation to json for Entities
included Entity instead of its subclass EntityTest in Layer
stub definition of fromJson in Entity
added dedicated getter and setter for zIndex
read zIndex from json
read state from json
added fromJson to AnimationSheet
added fromJson to Animation
added fromJson and toJson to TextureMapping
added fromJson and toJson to Texture