Implement Support for "Hermite EETF" as per "BT.2390-4".

[sobotka]

To round out the functions of HDR support, the final piece seems to be the EETF for dynamic range compression as given on pages 20-21 of https://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-BT.2390-4-2018-PDF-E.pdf

[KelSolaar]

Coincidentally, I just came across this on DisplayCAL: https://sourceforge.net/p/dispcalgui/code/HEAD/tree/trunk/DisplayCAL/colormath.py#l2920