Blender Git Loki

Sculpt: Add color alpha controls to the brush cursor

Previously the alpha was hardcoded to 0.7. Now it is possible to control
the cursor alpha by changing the alpha color of the cursor color
property. New alpha default is 0.9. This, with the new saturated colors,
should make the cursor more visible on highdpi screens.

I also removed the cache location preview as it is too visible right now
with the new alpha and color values.

Reviewed By: billreynish

Differential Revision: https://developer.blender.org/D6433