Make Antenna::transform_to_local_direction a protected method
Make Antenna::transform_to_local_direction
(https://git.astron.nl/RD/EveryBeam/-/blob/master/Antenna.cc#L6), this would allow to re-use this method in BeamFormer::transform_to_local_position
(https://git.astron.nl/RD/EveryBeam/-/blob/master/BeamFormer.cc#L15), thereby saving a couple lines of code