refactoring of show code to increase robustness of error checking when opening dsobjects and filepaths
refactoring of show code to increase robustness of error checking when opening dsobjects and filepaths

walterbender/turtleconfusion,walterbender/turtle3D,walterbender/turtleflags,walterbender/AmazonasTortuga,walterbender/turtleartmini,AlanJAS/turtleart,walterbender/turtleart