Updated error handling in SceneDirector#add
Updated error handling in Preloader constructor and Preloader#start
Added Localization#exists to check if a localization property does exist
Added localization property for AchievementManager
Restructured localization module
Added localization group
Allow localizable achievements, fixes #28
Updated break condition
Better default value for this.template.source in lyria/scene
Added getter for Viewport.$element, removed stubs as it's not need at the moment
Updated generated files + other stuff