Dr. Geo update, Cuis port

I am porting Dr. Geo to Cuis-Smalltalk. I am doing that because with Cuis, it is not too difficult to understand how large parts of the system is working. This is important when you need to understand the behavior of some features of the system, or when you want to extend the behavior of some classes.

Moreover, the Morphs system of Cuis -- the GUI part -- is a largely improved and simplified version of Morph as found in Squeak or Pharo. Writing new Morph has never been easier. Next, the behavior of Cuis is very predictable, it really ease the programming experience, it is notably important for me as I can only dedicate small chunks of time to develop Dr. Geo.

The port is still work-in-progress.