effective deltaT or old time for lumpedPointMotion

As discussed off-line with @Taka, it would be useful to also record information about the update period to pass through to the FEM code.

Eg, Instead of the forces.out containing this

// Time index=421 value=0.08421 

points
...

it would be useful to have it contain

// Time index=421 value=0.08421 updateInterval=0.004

This is because the OpenFOAM mesh update interval can be controlled by just about anything (timeStep, cpuTime, clockTime) and the FEM code has no convenient way of obtaining this information, other than having its own internal cache.

Taka provided modify_force.out_file.pdf in the explanation.