Refactor the Line, Rectangle, Ellipse, and Polygon tools into a unified Shape tool

[0SlowPoke0]

Replaced the existing Line, Rectangle, Ellipse, and Polygon tools with a unified Shape Tool that supports the creation of all these shapes from a single interface. The old Line, Rectangle, and Ellipse tools have been aliased to use the new Shape Tool. In addition to shape creation, the new tool also supports modifying the shapes it creates.