Enhancement: provide extension that updates ModelAdmin's getEditForm()

[wernerkrauss]

As ModelAdmin provides a hook "updateEditForm" it would be great, to add an extension to a module's ModelAdmin to get drag-and-drop sorting functionality easily.

I normally use this gist in a subclass of modeladmin:

https://gist.github.com/wernerkrauss/e49898de328ec469877bb32e202c6028