Gridfinity Baseplate OpenSCAD Remix

This is a minor remix for Jamie's OpenSCAD Gridfinity baseplates.  When I printed the original baseplates, they included surprisingly sharp points that I believe were geometry artifacts.  I just sliced them off by subtracting a new cube on the top.  You can select whether or not you want this effect by changing the boolean variable croptop.

I subtracted a new block from the top of the baseplate to slice off some very sharp protrusions that were printing on the baseplates.