
Nodeable can not get married with his sister, mother, aunt, daughter, grandmother, granddaughter
aa.aa.aa ----->>    aa.aa.ab
...
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nodeable that is not yet a node, can not create nodes.

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Deleting nodeables and nodes

$node->detachFromTree() // This will not delete nodeable model, but node model with 
                        // its descendants node
$node->toggleGender()
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$node->moveTo($node||$location)
$node->moveChildrenTo($node||$location)
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$node->deleteChildren();
$node->delete();
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Adding main node class to main node when building the tree.
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Tree::nodesOnTop()
not working correctly
    it return all nodes
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fix method Nodeable::deleteAndShiftChildren()
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Add pasteTree($tree) method to Nodeable class
    this method will copy a tree and paste it to a node
    to make the root of the given tree as child for
    target node.
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add method addCssClassToNode($class, $id)
    $class = css class name
    $id    = id of the node to apply css class on
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