Add unlink clone checker. - Monitor changes of DOM-tree of the document - Unlinking a clone is actually removing the clone and copying nodes from the source. - Copy value of ID of a node to saved_id to track source of copy nodes. - For a new node with 'saved_id' is a copy of another node. - Copy vulae of 'saved_id' to 'ns0:duplicate-src' to keep the source - Change value of 'saved_id' to the value of ID of the node for later copying. - For a new node without 'saved_id' is not a copy of another node. - only set 'saved_id' to the value of its ID.

.tree .tree-checkbox li a, 
.tree .tree-checkbox li a.unchecked {
	background-image:url("check_0.png"); 
}
.tree .tree-checkbox li a.undetermined {
	background-image:url("check_1.png"); 
}
.tree .tree-checkbox li a.checked {
	background-image:url("check_2.png"); 
}
.tree .tree-checkbox li a.clicked,
.tree .tree-checkbox li span.clicked {
	background-color:transparent;
	border-color:transparent;
	color:black;
}