Add side mirrors to bounding box

[ClemensLinnhoff]

Describe the feature

Add side mirrors to object bounding boxes to avoid confusion about what the contents of the object bounding boxes is. A bounding box without side mirrors can still be given with the recently added sub-bounding boxes.

Describe the backwards compatibility

This will break backwards compatibility since it changes the current definition of what an object bounding box contains. Therefore it can only be implemented in a major release.