Added 'hex8' format, for working with RGB + alpha transparency in 8 digit hex


* Hex values from 0.0-1.0 are translated into 0-255, then converted to a hex string
* Example: #AABBCCDD is RGBA(170, 187, 204, 0.87) -- ("dd" == 221, 221 / 255 = 0.8666 ~= 87%)