Remove standalone exhibitor page

[AugustPaulsrud]

Remove the page for individual exhibitors. All the information contained on theses pages is identical to the information contained in the popup/drawer of the exhibitor list. Ex https://armada.nu/student/exhibitors/1327 has the same info as https://armada.nu/student/exhibitors?id=1327. This task includes removing the first of these two as a page and any code that is no longer needed.