Fix mass properties.
Fix mass properties.

elen4/simbody,Gjacquenot/simbody,elen4/simbody,robojukie/simbody,elkingtonmcb/simbody,elkingtonmcb/simbody,Gjacquenot/simbody,chrisdembia/simbody,Gjacquenot/simbody,chrisdembia/simbody,scamille/simbody,simbody/simbody,robojukie/simbody,scamille/simbody,robojukie/simbody,scamille/simbody,chrisdembia/simbody,simbody/simbody,elkingtonmcb/simbody