New way of making stretch sprite. Origin is at 0,0.5 rather than at center
of sprite (0.5, 0.5). This allows accurate scaling over the x-axis.

This sets up future code to be able to accurately draw a triangle rather
than a circle to stitch between endpoints.

	modified:   Assets/Code/Drawing/Layer.cs
	modified:   Assets/Code/Drawing/Sprite3D.cs