Blender Git Loki

Sculpt: Sculpt cursor UX improvements

This commit introduces the following changes:
- Invert the direction of the brush strength WM control. It was working in the opposite direction to any other control in Blender. Now dragging to the right increases the strength.
- Increase the alpha of the cursor
- Remove the font shadow of the numbers in the WM control. It was adding too much visual noise when rendered on top of the brush alpha
- Add a second circle to preview the strength in the cursor
- Increase the resolution of the cursor circles. Now they look smooth even when working with large brush sizes.
- Add a line preview to display the brush curve
- Don't offset the cursor preview when changing size and strength

Reviewed By: billreynish, brecht

Differential Revision: https://developer.blender.org/D5889