Rotation wraps points too eagerly

[SimonN]

Version 0.3.0.

• Have a torus map that is very large in one dimension, and small in the other.
• Scatter pieces throughout the map.
• Select all pieces. Hit rotate 4 times.

Expected: No operation, because rotating 4 times is a full turn rotation. Observed: The pieces have been clustered into a small square-ish heap.

Try to wrap points only when saving the level. Maybe wrap already when the selection is cancelled?

[SimonN]

Since #56 Undo in the Editor, tiles must wrap at all times to satisfy the invariant of the undo buffer.

If we really want to implement this #71, we'll have to track unwrapped coordinates separately (probably in the tiles?), and also make that information known to the rotation (subtype of Undoable). This will be hard for comparatively small gain.