Problems with rotation (translation seems to work), although slider bars would work better for the
interface.

The interface needs a "ge_icp" button, once translation maximizes overlap.
I would also need a way to identify points of overlap.
For each point of cloud 1, compute nearest distance to cloud 2 and remove points whose distance
is greater than 0.05 (5 cm).

So I need two buttons: "crop" and "do_icp"