new Geometry.OCCSafeUnbind to disable fast unbind optimization (e.g. for tag backward compatibility): cf. #1928

handle degenerate case when the same element touches both sides of the same crack with different nodes

tutorial/ -> tutorials/

initializing the api now sets General.Terminal=1 (to print messages by default) and General.AbortOnError=2 (to throw an exception as soon as an error happens) - cf. #1043