Implement Phase tracking module in solution operators

Short description of desired functionality:
A module that uses a waveform definition as variable and calculates the integral \int \vec{G}\cdot\vec{r} dt for a given trajectory per material point

New definitions:
New module solution_operators.phase_tracking

Implementation Idea:
Start with left-side rectangular integration and a time-grid definition of the wave-form that equals the trajectory time-grid.