Add rotation sliders to armature widget

The rotation sliders allow the user to interact dynamically with the bones.
If the users selects another bone, the rotation returns to 0 and the
previously selected bone keeps the last transform applied to it.

See Issue #13980
Have double cone representation dependent on the vtkBoneWidget transform

This have the representation turn on itself when the bone is moving.

See issue #13980
Have cylinder representation dependent on the vtkBoneWidget transform

This makes the representation turn on itself when the bone is moving.

See issue #13980
Merge branch '13980-RotationSliders' into armatures

* 13980-RotationSliders:
  Have cylinder representation dependent on the vtkBoneWidget transform
  Have double cone representation dependent on the vtkBoneWidget transform
  Add rotation sliders to armature widget