Add utility to load trajectory from file

[dokempf]

This should first define a numpystructured dtypefor the trajectories and then provide a utility that loads it - effectively a thin wrapper around numpy CSV loading.

API:

@validate_call
def load_trajectory(
	trajectory_file: Path,
	tIndex, xIndex, yIndex, zIndex, rollIndex, pitchIndex, yawIndex,
	trajectory_separator, radians
):
	pass