While fixing the above, add methods to physical body and shape pointer
wrapper so routines won't have to know that IntPtr.Zero means no
physical instance.
Fix problem with physical linksets failing after a few sits and
unsits by properly restoring child prom positions for compound
linksets after multiple selection and deselections.
static objects by more restrictive selection of objects that collide
with static objects.
Rename collision mask fuctions from 'filter' to 'group' so it is clear
what is being set.
Rename BulletSimAPI.SetCollisionFilterMask() to SetCollisionGroupMask to match above.
Restore passing of time step to linear and angular motion component routines.
Use buffering vehicle physical parameter get/set routines consistantly.
Make range enforcement clearer by using ClampInRange() function for parameter setting.
Remove commented out experimental vehicle calculations.
Robert Adams