Add support for LCh color space to UIColor

[mpospese]

Add a UIColor initializer that supports the LCh color space.
This will require importing a couple of gists to support CieLAB colors but also creating a new "friendly" UIColor initializer to refer to the CieLAB version internally.

public func init(luminance: CGFloat, chroma: CGFloat, hue: CGFloat)

where luminance is 0.0 – 1.0
chroma is 0 – ~180
hue is in degrees not radians