regenerate Y from V as follows.
Y = 1.1913*V - 0.22532*V**2 + 0.23351*V**3 - 0.020483*V**4 +0.00081936*V**5

Makefile (munsell-data.el): complement gray data.

munsell-conv.el (munsell-split): support the form `Nvalue'.
(munsell-round9: ditto.

munsell-conv.el (munsell-split): recognize Nv/c format.

munsell.el (munsel-resolv-property-face): new function.
(munsell-resolv-properties): ditto.
(put-text-property): adviced.
(add-text-properties): ditto.
(set-text-properties): ditto.
(overlay-put): ditto.

munsell-conv.el, munsell.el: combine hue-minor and hue-major.

initial version.