Resolve "Spectrometer trajectories"
Closes #3668 (closed)
For spectrometer items (i.e. detector + analyser):
add intermediate method over compute_bragg_solution to distinguish case where traj_mode is True
add load traj func
add move_traj func
add enable traj_mode func (check yml key at this moment)
add traj_axis key in yml
Note: if real_axes: => as usual else: if traj.position != None: bragg = traj.position compute( bragg ) => {xi} => plot, info else: grey plot + nan info