Add lightning and do some more refactoring

 * Add bpydoc settings
 * Add some more comments in the header
 * Add global settings
 * Make Projector more robust
 * Add SVG animation with javascript
 * Add lightning pass to Renderer
 * Split the main rendering routine into its passes
 * Improve the visibility routine
 * Add several helper routine to join objects or to do a object based
   depth-sort

Signed-off-by: Antonio Ospite <ospite@studenti.unina.it>