Adds brush as a decal to the cursor

[TokisanGames]

• Adds the current brush as a decal to the cursor.
• It is scaled and aligned with how the brush will affect the terrain.
• If jitter is high, the brush will spin like a drill bit as it paints the ground.
• Advanced option to hide brush decal while painting (see drill bit)
• Decal opacity matches brush opacity down to a minimum of 33%.
• Different modes have different colors. e.g. Sculpt raise is white, lower is black, flatten is dark cyan, roughness is light cyan, texturing is green, and the colormap is whatever color you have selected.
• Pickers use a smaller circle brush (ring1)

Fixes #62
Only one commit 03fd1bb
Based off of #91 , merge that first