Improvements to Blenders color balance (lift/gamma/gain).

Fairly closely match some mac application colin has called 'Looks', to give better results.
- lift is now applied non linear (was being added to the color)
- change the color wheel to preserve the luminance of the gamma and gain values, this stops the color from being set too dark (option for the color wheel template).
- sub-pixel precission for the color wheel since the white area at the center can make a lot of difference with a very small change.

This change will make existing node and sequencer setups lift render slighly differently however discussed this with Ton and he's ok with it.

release/scripts/ui/properties_physics_common.py

@@ -38,7 +38,7 @@ def point_cache_ui(self, context, cache, enabled, cachetype):
     col.operator("ptcache.remove", icon='ZOOMOUT', text="")
 
     row = layout.row()
-    if cachetype in {'PSYS', 'HAIR', 'SMOKE'}:
+    if cachetype in ('PSYS', 'HAIR', 'SMOKE'):
         row.prop(cache, "external")
 
     if cache.external: