#258 Eraser fill

[William Kendrick]

A new mode of either the Eraser or Fill tool that does a flood-fill-based erase to expose the background (color, starter background, or template).

(If as part of Fill, this would be rather than doing a solid (or gradient) color fill using the chosen color. If as part of Eraser, this would be one-click way to erase a homogeneous area, versus having to click and drag to erase freehand.)

[William Kendrick]

Done!