When updating an image, it now creates a new Image() instead of just setting the src. This should fix the problem I would have had with assets not being drawn while they were being updated.
onclose (mainScreen toggle fix)
Fixed annoying selection of the main canvas / the body / html.
Replace color tool; Resize canvas; undo/redo
Made art manager look a tiny bit nicer.
gui.active keeps track of the active modal... used by an earlier commit :(
Uploading done. (Python is awesome.)