public AddStageViewModel(ITilesetDocumentFactory tilesetFactory, IDataAccessService dataService)
{
_tilesetFactory = tilesetFactory;
_dataService = dataService;
ViewModelMediator.Current.GetEvent<ProjectOpenedEventArgs>().Subscribe(ProjectChanged);
AddStageCommand = new RelayCommand(AddStage);
BrowseTilesetCommand = new RelayCommand(BrowseTileset);
BrowseTilesheetCommand = new RelayCommand(BrowseTilesheet);
CreateTileset = true;
}