Improve RGB/HSV implementation

[Groovounet]

http://chilliant.blogspot.com.au/2014/09/rgbhsv-in-hlsl-6.html

[Groovounet]

http://www.chilliant.com/rgb2hsv.html

[Groovounet]

https://docs.opencv.org/3.1.0/de/d25/imgproc_color_conversions.html

[Groovounet]

http://lolengine.net/blog/2013/07/27/rgb-to-hsv-in-glsl