Renames VirtualToolCoupler's attachment to attachmentPoint.
Renames local variables for clarity, in VirtualToolCoupler::update.
The variables are related to the attachment point.
Renames inputMassCenter to inputPosition to match with objectPosition,
both are world frame locations of the mass center calculated with
different poses.
Renames orientedAttachment to leverArm, because it is only used to
calculate torque from force at a distance.
VirtualToolCoupler's attachment point is now a local coordinate.
Previously it was the vector from the mass center to the attachment
point. This approach is simpler because for a mesh shape the user can
use a mesh visualizing program to find the local coordinate they need
for the attachment point, without worrying about where OSS may
calculate the mass center to be.
Replaces setSubMatrix with Matrix.block in VirtualToolCoupler.
Also a bugfix in which block dTorqueDposition and dTorqueDvelocity
belong.  The equation for the springJacobian is:
[dForce ] = J * [dPosition   ]
[dTorque]       [dOrientation]
So dTorqueDposition goes in the bottom left block.
Use linear() to rotate vectors, instead of rotation(), in VTC.