!! NOT STABLE !!
Initial implementation. No UI update yet.
Check js/model/Piskel.js and js/model/Layer.js for an overview of the new
API.
Piskels can be saved on the existing service.
Previous piskels cannot be loaded. This should be fixed soon.
* new file : HistoryManager.js
* can undo (ctrl-z) and redo (ctrl-y) changes performed through the
tools
* history states are recorded per frame
* a new state is recorder each time a tool is released (introduced
TOOL_RELEASED event for this purpose)
* a duplicated frame doesn't inherit the history states of the original
frame
* there is no limit to the number of states that can be stored per frame
* actions such as creating/duplicating/deleting a frame are not
concerned by this update