recommend use of new style axes (canSAS-like) in NXdetector

[zjttoefs]

For detectors with multidimensional data axes are obviously useful, even if the detector is not the one providing the default plottable data in NXdata.

NXarpes already makes use of that.

[zjttoefs]

This requires #369

[prjemian]

Might not be required for a NXdetector group. The axes attribute is for the NXdata group

[prjemian]

This was missed by the 2020-2 code camp

[prjemian]

Also missed at 2022-06 code camp.