Simplified the prescribed values of the _space_group_magn_transforms.source tag (to BNS and OG).
Substantially edited the explanations associated with the _space_group_magn_ssg_transforms.source tag and added a new value (ISO-MAG).
Minor edits to the references for many transformation-related tags.
Simplified the prescribed values of the _space_group_magn_transforms.source tag (to BNS and OG). Substantially edited the explanations associated with the _space_group_magn_ssg_transforms.source tag and added a new value (ISO-MAG). Minor edits to the references for many transformation-related tags.