ngDragClone ask too much configuration

[Shocoben]

Hi,

Don't you find that there is too much configuration to do to use the ngDragClone ?

I've added some features the ngDragClone and now it's super easy to have a drag clone which copy the draggable.

It's part of the pull request of @bastbnl fork.
bastbnl#1

• Now, when being hover a ngDroppable, the ngDragClone also gains the
  class "drag-over"
• Attribute ng-drag-clone-group="groupename" let your specify a group to
  link a specific draggable to a specific ngDragClone
• Now, the ngDragClone automatically copy the html and classes of the
  draggable.
• You can deactivate the copy with the attributes on both, the ngDrag
  and NgDragClone by using the attribute ng-drag-clone-copy-class="false"
  or ng-drag-clone-copy-html="false"
• Can add class to the clone by the ngDrag with the attribute
  ng-drag-clone-add-class="test"

You can look at the "example-multiple-scrolls.html" for more details.