Version 1.78 - Wider eraser

Version 1.78 - Wider eraser

The eraser was previously 25% larger than the pen. This was okay for drawing and erasing wide lines, but didn't really help for thinner ones, and it was probably too conservative.

The new eraser is 25% larger + 12 pixels in diameter. This should make it easier to spot-erase work, while hopefully not causing problems for anyone.