Saving and restoring a map draft

[ufdada]

To save the progress of a map for unpredictable situations (browser-crash, accidental tab closing etc.) the mapeditor should be smart enough to set and reset a draft after every action.

Sideeffects: As the browser has a max of 5MiB to store, i just would store one map as draft (no undo/redo - data).

Actions where a draft should be

set	reset
after setting a tile	generate new map
redo	import map file
mirror map	import csv file
resize map	export map
undo	choose cancel on confirm message

Edit: There is no confirm message, the map file gets immediately restored now. It is more convienent that way.