PrescribedForce cannot get force, point and torque if rename FunctionSet

[mitkof6]

If one changes the names of the FunctionSet for the force, point and torque in the PrescribedForce component, then they are not recognized correctly.

For example, the FunctionSet for the force should be defined:

<FunctionSet name="forceFunctions">

if it is defined with a different name:

<FunctionSet name="force_functions">

then it is not recognized thus applies zero force. The same holds for the point and torque.