xili-language version includes fixes and integration of optional plugin xl-bbp-addon (used with multilingual bbPress)

• integration of xl-bbp-addon (no more a plugin),
• fixes/adds ‘menu-item-has-children’ class in menus built by selector (as used in twentyfourteen / twentyfifteen theme css for sub-menu on left sidebar to show small arrow),
• fixes propagation options,
• better management of dashboard language and user profil (thanks to Renoir),
• selected value of languages in general settings set to get_option(‘WPLANG’) (and not filtered locale).

M.