Added Morsy, a new lightweigth robot model for testing

The model may be used for education material or MORSE demos for
instance.

Based on the official MORSE mascott ;-)
Thanks to Michael Karg for the initial Blender version
[builder] Minor improvement to error msg when a model is not found
[doc] Mention Morsy in the new features of future 1.1
[sensors] print frequency on initialization