PR: Implement support to generate the "Rösch-MacAdam" colour solid hue lines.

[KelSolaar]

This PR implements support for the argument I described in @scooperly's Sketches of Hue thread on ACEScentral.

I remembered about it only because I started to look at @gutenzwerg's work in #768. Note that #768 is different in the sense that the Optimal Colour Stimuli are computed for a given luminance level.

Sean produced a not-insignificant amount of work and our implementation of the CIE XYZ outer surface could/should have covered that with a few minor changes, namely the pulse waves ordering.

import colour

figure, axes = colour.plotting.plot_chromaticity_diagram_CIE1931(
    standalone=False)

bins = len(colour.volume.spectrum.SPECTRAL_SHAPE_OUTER_SURFACE_XYZ.range())

xy = colour.XYZ_to_xy(
    solid_RochMacAdam(
        point_order='Pulse Wave Width', filter_jagged_points=True)[1:-1])

for i, j in enumerate(range(0, xy.shape[0], (bins - 1) // 2)):
    hue_lines = np.vstack([xy[j:j + (bins - 1) // 2, :], xy[-1]])
    axes.plot(hue_lines[:, 0], hue_lines[:, 1], c='k')

colour.plotting.render()

I will merge as soon as tests pass and put the above code in the How-To Guide and on ACEScentral.

[coveralls]

Coverage increased (+9.0e-05%) to 99.724% when pulling d1cca65 on feature/rosch-macadam into 362ccee on develop.