Added sixDoFRigidBodyMotionSolver using septernion interpolation for mesh-morphing

This reverts commit c5bea524.

This reverts commit b18f6cc1.

Removing rhoInf from uncoupledSixDoF... patch, not needed.  Adding
optional rhoName entry to sixDoF... so no rhoInf entry is needed for
simulations that have a rho field, and require than a rhoInf value is
read for those that don't.

position of patch points.  Adding autoMap and rmap functions to
correctly handle p0 on decomposition and reconstruction.

restraints and constraints.

Moving sixDoFRigidBodyMotion back one directory.

Adding uncoupledSixDoFRigidBodyDisplacement to execute motion
specified by the six DoF motion state, but not applying surface
forces.  Useful for pre-displacing a mesh.

Adding constrainedSixDoFRigidBodyDisplacement to temporarily perform
Vorticity's lander simulation.  Will be removed when generalised
constraints are added.

dependency on the libforces.so and the libraries it requires.