* Add property in OpenSpaceEngine for fading duration when enabling / disabling
* Add interface for fadeable components and apply to renderable
* Make layers a fadeable component
* Make globelabels a fadeable component
* Make labelscomponent a fadeable, and give it an enabled property
* Make screenspace renderables fadeable components
* Introduce concept of parent fadeables, to fade out subowners with parent
* Make rings fadeable as well
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Co-authored-by: Alexander Bock <alexander.bock@liu.se>
