big refactoring:

- renamed Vector3D -> Vec2
- replaced (double x, double y) by Vec2
- many many name changes
- rm initAttributes
(currently non functional!!)
commit to revert
fixed rf bugs
commit before optimization
improve exec time by removing pointer dereferencings
cached last hit pixel to stop large O(N²) search
changes
changes: monte carlo
Merge pull request #2 from froed/master

Refactoring