Rework force models and central moments transform
This MR provides a complete rework of the force model, so they are functioning in the moment space and the central moment space.
Furthermore, a new implementation for the shift matrix is provided and a rework of the central moment based method.
The central moment transform classes are adapted to be able to work with the changes.
- Test Fixed Density BC when method has a force model
- Forward/Backward Transform for D3Q15
- make cumulants aware of polynomials
- rework cumulants with force