Clarify XML comments regarding coordinate motion type and units

[aymanhab]

In 4.0, we do not expose motionType for a coordinate but the XML file still contains values (default, range) that could be converted to angles if underlying motion type is considered rotational and not converted otherwise. Current comments refer to translational and rotatioanl coordinates but leave coupled ambiguous.

[aymanhab]

Comments refer to meters and radians