Rename function, use protected
Add javascript listeners only once
Improve recursive search for image enlarge dimension, use correct access-level

Fix for: 464095029eca097d46fd15ff71e01f3c16d2f9a0
Set listener on afterRender to be initialised everytime
Set previewImageUrl only if every needed parameter existing to prevent error on load
Rename function to be more descriptive

Fix for: dbffc4bacaa373215c1388a13931adae5a751638
Add _ to show this shouldn't be used from outside
Add new german translation