[ODE] Contribution to the documentation (in the wiki)

[Remi Ricard]

Hi,

I did some modification of the wiki  (added some missing tables).

But now I want to add some info about the universal joint.
- Default axis value (should go into the Manual-> Joint Type and 
Functions -> Universal section)
- Why I'm getting "zero length vector" when there is only one body 
attached to the joint. (I don't know where this should go)
(Try:
  universal->attach(0, bodyID);
  universal->setAxis1(1, 0, 0);

The answer is: Ode swap the body to the first position when there is
only one body and also swap the axis order so
The Default axis axis1 = (1, 0, 0); axis2 = (0, 1, 0); are swapped.

So the call universal->setAxis1(1, 0, 0); set axis2 to (1, 0, 0)
and then you try to do the cross product between
(1, 0, 0) the axis 1 you have set
(1, 0, 0) the default axis1 swapped with the second axis because
           of the "one body on joint"
The resulting cross product is (0, 0, 0)
)


Remi