Undo function

I recently screwed up my map of Sandpoint by trying to "resize" it* and not saving it before. All my map markers' placement got messed up by that. No CTRL+Z to undo it. Needless to say I was very sad.

So: please implement an undo function to reverse the last (few) things you changed on the map.

This suggestion in Google Moderator: http://goo.gl/mod/6JRz


* I wanted the grid to be smaller and tried the function to expand the map.