Nearest Clone

Finds the distance to the nearest clone.

I wrote this after someone described what the process would look like using Scratch (creating lists of clone coordinates and writing code to calculate distances.)  I called it "Scratch microcode" and wrote this small test case to avoid that.

Many Scratchers have asked for native way in Scratch to allow the blocks to work with a specfic clone.  So here it is (but for Snap).