Basic cup should be centered

[Russ Nelson]

If you create a basic cup with any values other than 1,1 only the first grid unit is centered. The whole module should be centered.

[Russ Nelson]

I suggest this because the largest glue stick you can hold without overlapping the edges is 34mm. Bigger than that, and it needs to use a 2x2 storage unit to hold the stick, but the basic cup isn't centered.

[Jamie]

I've updated grid block to have an option to center the assembly in X/Y (but not Z), somewhat analogous to the option in the native OpenSCAD cube(). 7a81cb2