[ODE] New test file for Joint PR

[Remi Ricard]

Hi,

Since yesterday there was talk on the list about new test files and 
after some discussion with someone trying to use the joint I created and 
after been told twice by David Walters to create a file to display what 
is the use of my new joint (Since he has no idea what this joint is 
doing ;-) ).

I created a test file displaying the behavior of the joint PR.


The joint is simply a slider with a Hinge with out the body between the two
Ex:
body -> slider -> body -> hinge -> body

body -> joint PR -> body

Less equation to solve == faster rendering


Remi