Re-order interface / method

[dantleech]

CMS resources are orderable, in addition to the EditableRepository methods we need to be able to change the order of resources.

I currently suggest adding this to the CmfEditableRepository interface being added in #17.

public function reorder($sourcePath, $destPath, $before = false);

or

public function orderBefore($sorucePath, $destPath);
public function orderAfter($sourcePath, $destPath);

[dantleech]

Done!