Adding a new rigid body to the world

In cram/cram_3d_world/cram_bullet_reasoning/src/objects.lisp:

(defmethod add-object ((world bt-world) (type (eql :liquid-minor)) name pose
                       &key (mass 0.00001) (radius 0.01) color)      
  (make-item world name (list type)
              (list
                (make-instance
                    'rigid-body
                  :name 'waterdrop1 :mass 0.00000000001 :pose (ensure-pose pose)
                  :collision-shape (make-instance 'colored-sphere-shape
                                     :radius radius :color color))
                )))