Move vertices to origin

Models with a large displacement from the origin (close to or larger than MAX DOUBLE) causes
problems in the viewer when the DOUBLE values are converted to FLOAT in the OpenGL call. We resolve this by translating the tesselated vertices to the origin, i.e. translating with the center of the bounding box of the model.

Currently this functionality is added to goview_vol_and_lr only (i.e. not goview). The translation is not performed by default but is accessible through View->"Move vertices to origin". And the translation may be reversed by calling View->Reset.

Currently only surfaces are handled.