`gui/design` stamp mode candidate

[MagistrumT-T]

Adds a "Copy Designated Tiles" command(Ctrl+v) that creates a shape mimicking the designated tiles under the current shape using a new shape called "Point Drawing", which just returns it's marks as the shape. It then starts "Stamp Mode", which is just center dragging but left click commits the shape instead of putting it down.

The command becomes available only when the user is not placing marks, forcing it to be used only with Auto-Commit off, which I suspect will make it hard to find on it's own, but possibly a way to introduce more users to all the functionalities of gui/design.