Gamut Compress v0.7

• Update compression method to use a parabolic function.
  See this acescentral post for details. See this desmos plot for a comparison with the previous Power(P) compression function.
  
• Advantages of the parabolic compression function
  • More even distribution of compressed values between threshold and distance limit.
  • More robust inverse transform.
  • Works much better at threshold values closer to the gamut boundary, so it's easier to leave surface colors unaffected.
• Remove shadow rolloff, since the parabolic compression curve fixes the invertibility issues it was trying to prevent.
• Add distance presets for common digital cinema camera source gamuts in Nuke nodes.