Fix for mobile menu not closing on login / register, hide search if not allowed

Baris, I looked at your change and wasn't sure if you intended to make the login / register links in the mobile version not under a submenu any more (I preferred it) but it wouldn't close the menu when you clicked on either login or register. I took the original code in the header template and wrapped the visible-xs registration item with the conditional tag that would hide the registration link if not allowed. 

Also now if search isn't allowed by guests, it won't show up.