D27017: [KColorUtils] Add hue(), chroma(), getHcyColor() and update documentation

[Noah Davis]

ndavis marked 3 inline comments as done.

REPOSITORY
  R273 KGuiAddons

REVISION DETAIL
  https://phabricator.kde.org/D27017

To: ndavis, #frameworks, dfaure
Cc: mwoehlke, broulik, kde-frameworks-devel, LeGast00n, GB_2, michaelh, 
ngraham, bruns