Rewrite tuple classes.
Rewrite tuple classes.

Simplify tuples classes generation. They are now also regular instances.
This was done to be in sync with code snippets presented in the user
documentation.

    * share/urbi/tuple.u: Here.

urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi