Step 1: Renamed SLNode into SLSceneNode
2. Step New SLNode
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Revert b761ca8..f6d2263

This rolls back to commit b761ca8de70a43dfac9fe51243f31c2fd651bf1e.
Added animation icons
Fixed wrong fps calculation
Fixed error on closing the qtViewer app
Fixed fps problem in qtViewer app
Merging master -> feature-animation
Dark style for gui. Updated animation widgets.