+ - Fix Arc manipulator. Idea: split edge handles so that the inner half controls
+ arc sizing, outer half controls rotation. That way you can grab either handle
+ and know what it's supposed to do.
+ - Fix loading and saving code
+ - Add Drawing Properties dialog (separate from Application Settings)
+ - Trim/Slice tool (to be able to click on a line segment crossing another, and
+ remove it and it only, or to cut the entity at other entities crossing)