Working virtual tile u/v editing!
TileShapeEditor improvments

Added user-controlable grid size.
Snap to the nearest grid point using qRound() instead of qFloor().
A face is selected by clicking inside its polygon.
Added Zoomable for controlling the scale of the scene.
Save/restore settings using QSettings.
Write shape data to virtualtilesets.vts.
Added shading to west-oriented faces when generating virtual tile images.
Use old iso tile image (if available) when a virtual tile has no shape.
Removed unused code.
Fixed VirtualTilesetDialog iso tiles list resetting the scroll position.
Added xy/z movement cursors to shape editor, delete-face button.
Mass renaming of TileShape::Element -> TileShapeFace.

Don't like nested classes, yo.
Added EnflatulatorDialog.