Introducing DUO.

The code has been forked. SXS 3D CNV is now conformed by two scripts
depending on the desired usage. SOLO and DUO. They differ on the fact
that DUO draws on two canvases, and has the initial ability to
dynamically create path elements. As of today, DUO can behave exactly as
SOLO, but SOLO does not implement all the functionality of DUO (Paths
specifically).