NXtransformations adds units attribute to vector attribute

[prjemian]

This is an error (in both HDF5 and XML).

Neither HDF5 nor XML attributes can have attributes themselves. As-is, this would result in a specification where a data file would specify a vector attribute which would, by the specification now, have a units attribute which could be assigned a value compatible with NX_DIMENSIONLESS.

[prjemian]

Here is the code with the error:

	<attribute name="vector" units="NX_DIMENSIONLESS" type="NX_NUMBER">
		<doc>
			Three values that define the axis for this transformation.
			The axis should be normalized to unit length, making it
			dimensionless.  For ``rotation`` axes, the direction should be
			chosen for a right-handed rotation with increasing angle.
			For ``translation`` axes the direction should be chosen for
			increasing displacement.
		</doc>
		<dimensions rank="1" value="3" />
	</attribute>

[prjemian]

Because is a design error that interrupts validation, it is high-priority to resolve.

[prjemian]

suggest adding a vector_units attribute to provide the requested information

[zjttoefs]

The documentation clearly states that vector is dimensionless. A units attribute is not required.