Added PaginatorHelper::sort support to BbTableHelper thead columns

As requested in issue #5.
Working as the following:

echo $this->BbTable->render(
			$dataFiles,
			array(
				'columns' => array(
					'id' => array(
						'label' => __('Id'),
						// Options for PaginatorHelper::sort() method (third parameter) - begin
						'paginator' => array(
							'direction' => 'desc'
						)
						// Options for PaginatorHelper::sort() method (third parameter) - end
					),
					'label' => array(
						'label' => __('Label'),
						// Complete turn of pagination for this column - begin
						'paginate' => false,
						// Complete turn of pagination for this column - end
					),
					'size',
					// For actions column Paginator::sort() parsing is turned off
					'actions' => array(
						'label' => __('Actions'),
						'items' => array(
							'view',
							'edit',
							'delete' => array(
								'confirm' => __('Entry will be deleted?')
							)
						),
					),
				),
			)
		);

The whole Paginator::sort() parsing takes place AFTER! the label was obtained by whatever method. This will not break any existing applications and all other modifications not already implemented can be applied.
$label will be used as second parameter of the Paginator::sort() method.