Improve selection.

Add ability to select only one category of objects in a zone.
Disable faulty modules on start-up.
Replace `orthonorme` parameter with more general `ratio` parameter.

TODO: there is no user interface currently.
Double click on an object to edit properties.
Rewrite of mouse events gestion and selection in canvas.
Major enhancement of selection mode.

User can adjust selection zone now.
Events management code was also slightly refactored and comments were added.