Consistency with terms: "atCoordinateSpace"

Replace "coordinateSpace" attribute by "atCoordinateSPace" for
consistency with the terms sheet.
Consistency with spec: "CustomMask"
Consistency with spec: "SearchSpaceMap"
Consistency with spec: "SubVolumeMap"
Merge pull request #59 from cmaumet/termUpdatesForSpec

Merge: (minor) term updates for consistency with terms and specification