Skip grab saver for unjointed bodies

[rschlaikjer]

• When grabbing a body with a body that has no joints, we can skip saving the current state of the body since all links are effectively rigid, and so would be excluded from the results of ComputeListNonCollidingLinks (all links are rigidly attached to the grabbing link)
• It doesn't look like we need to save velocities at all for the ComputeListNonCollidingLinks savers (has no impact on collision?)
• Convert a couple of shared pointer copies to shared pointer references in ComputeInternalInformation