Grid subset of LayerData
offsetY:Int
offsetX:Int
name:String
gridCellsY:Int
gridCellsX:Int
gridCellWidth:Int
gridCellHeight:Int
@:optionaloptionalgrid2D:Null<Array<Array<String>>>
@:optionaloptionalgrid:Null<Array<String>>
arrayMode:Int
_eid:String