Workaround for incorrect frame selection after re-ordering on Firefox
Workaround for incorrect frame selection after re-ordering on Firefox

This commit is related to the following issue: #363

When a frame is dropped both `mouseup` and `click` events are triggered on Firefox. This is somwhat expected behaviour but other browsers do not trigger the `click` event.

One would expect jquery-ui to work the same across all browsers but when they got a bug report they decided to not change anything:
https://bugzilla.mozilla.org/show_bug.cgi?id=787944

The most comon workaround appears to be to use the `clone` helper in jquery-ui sortable. Unfortunately this doesn't work because the cloned frame doesn't keep the contents of the canvas. This seemed like the cleanest workaround, here are a few others:
http://stackoverflow.com/questions/947195/jquery-ui-sortable-how-can-i-cancel-the-click-event-on-an-item-thats-dragged

piskelapp/piskel,GMartigny/piskel,zoeesilcock/piskel,zoeesilcock/piskel,juliandescottes/piskel,piskelapp/piskel,GMartigny/piskel,zoeesilcock/piskel,smiegrin/piskel,juliandescottes/piskel,GMartigny/piskel,piskelapp/piskel,smiegrin/piskel,smiegrin/piskel,juliandescottes/piskel