Fixed M8 sizes, Added test object, Fixed OpenScad CommandLine

M8 sizes were wrong, split open when rod was forced in.
Added Prussa sizes, fits M8 well.

Added test object so user can ensure things fit before big prints.

OpenScad doesn't like loading wallice.scad on command line.
Put assembled machine in machine function, same for pulley.

Punched hole in end of X-Carrage so bars don't need to be exact.