[FIX] Fix links to manage structure (object) permissions on the wiki pages that are at the top of the wiki structure (they are internally handled as wiki page object for the box in the structure navigation bar to show up properly with local or category perms). Thanks Jonnyb for your feedback and code tips. Reverting also the addition in tiki_edit_structure.php of struct perms since this whole system of handling wiki structure permissions seemed to break previous behavior without upgrade script.