added parameter for sorting of pages

Added functionality to make it possible to sort the pages of the container
Using the parameter "order" within defined within each page. ordered from lowest to highest.

look:
                array(
                    'name' => 'second',
                    'properties' => array(
                        'uri' => 'http://www.child1.com',
                    ),
                    'attributes' => array(
                        'class' => 'child1-class'
                    ),
                ),
                array(
                    'name' => 'last',
                    'order' => 200,
                    'properties' => array(
                        'uri' => 'http://www.child1.com',
                    ),
                    'attributes' => array(
                        'class' => 'child1-2-class'
                    ),
                ),
                array(
                    'name' => 'first',
                    'order' => -1,
                    'properties' => array(
                        'uri' => 'http://www.child2.com',
                        'foo' => 'bar',
                    ),
                    'attributes' => array(
                        'class' => 'child2-class'
                    )
                ),