NX_COMPLEX - Update nxdlTypes.xsd

[sanbrock]

added NX_CCOMPLEX, NX_PCOMPLEX. NX_COMPLEX, and NX_QUATERNION

• closes NX_COMPLEX: a new NeXus data type for complex numbers #1056
• closes NX_COMPLEX (a new Nexus type for complex numbers) #1066

[mkuehbach]

xs:documentation have a typo in all four data types: should be "representation" instead of "representaion"

[prjemian]

@PeterC-DLS This is ready for review.

[prjemian]

View of published documentation:

[sanbrock]

NX_COMPLEX types are now represented as LIST of 2 doubles (in case of quaternions, 4 doubles). Trying to describe them as a proper compound type with labels, like 'r' for the real part and 'i' for the imaginary, one should define a SEQUENCE instead of a list.
This requires the creation and use of ComplexTypes instead of SimpleTypes for our 'primitiveTypes'. Unfortunately, complexTypes are not supported to specify the TYPE of an ATTRIBUTE which we need for defining the NXDL attribute 'type':
https://github.com/nexusformat/definitions/blob/1056-NX_COMPLEX/nxdl.xsd?#L764

[PeterC-DLS]

LGTM

[prjemian]

@PeterC-DLS Thanks for the review!

@sanbrock Merge when you are ready.