A Magic tool, similar to "Perspective" (which affects the whole canvas as a single large rectangle), but which provides a grid of control points which can be adjusted, allowing different levels and directions of distortion of different parts of the image.
Some examples I can think of:
* Drawing a picture, and then "wrapping" it around a cube
* Stretching the corners of a person's mouth to form an absurdly large smile or frown
See also "Image Warping Tools" (mesh-based effects using click-and-drag, which would have an effect closer to the "Smudge" tool): https://sourceforge.net/p/tuxpaint/feature-requests/239/
Considerations:
* I'm thinking back to the mesh controls provided when using a "morph" tool (think Michael Jackson's "Black or White" video)
* How best to deal with attempts to move one mesh's control point "through" part of the mesh grid (disallow? cause other control points to move automatically?)
