Fixed calcSystemMassPropertiesInGround() which was nonfunctional.
Fixed calcSystemMassPropertiesInGround() which was nonfunctional.

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