MEGHDF5: Apply transform when loading channel information
In naf/meg/meghdfreaders.py MegHDFReader::ensure_chaninfo we need to apply the system_to_subject transformation. During testing this does not matter as the converted 4D datasets have an identity transform but it will matter later on.
This is a simple matter of making sure that we transform both the positions and orientations correctly (remembering to keep the orientations as a unit vector)