trivial: Remove the '.csv' extension in cd-csv2cmf
Write the same format CMF files as ArgyllCMS

According to Graeme, the CMF files are unindexed and implicitly XYZ.
Also, rework the spectral API a little to be a bit easier to use.
[colord] Add cd_color_xyz_to_cct()
Generate the CMFs from source data
Install several standard illuminants

The Fx data is from http://www.rit.edu/cos/colorscience/rc_useful_data.php
and the others were obtained from https://github.com/ekmett/colorimetry.
colord: Add cd_spectrum_planckian_new()
Install the CRI Test Color Samples