Create lastEdit {}, implement .revert, conflict resolution

Use ALT key shortcuts instead of CTRL (less conflicts with browser).

Layers now contain both obj/func AND html version.
The html version is compared to what's on screen to know
if it was changed by the player.

.revert uses the stored html version to undo the changes.

Add message for unkwownCmd
Add message for layerModifiedRemotely

Refactoring:

onPressEnter > processChatMessage
cmdParts > cmdArgs
the lastEdit object groups properties that
had to be calculated each time before.