ENH: Propagate vtkMRMLSliceNode::ThreeDViewIDs to slice model display
STYLE: Add accessors to vtkMRMLCameraNode
BUG: Fix crash in models logic when failing to read file

The returned node was deleted if not added into the scene.
STYLE: Fix header copyright.
ENH: Factorize slice composite node search in vtkMRMLSliceLogic