updated navbar with AI, improved page links, edited ERT, Security, and Chaplain pages

This PR:

fixes several broken links in pages and makes referencing some pages cleaner.
updates the navbar with a link to the Station AI.
adds a section to the chaplain's page covering their null rod and holy book functionality. fixes #82.
fixes some typos here and there, and updated some small bits of advice that are outdated compared to modern unitystation.
removes some misleading text in the Detective's page that described game features that aren't in game yet.
reformats the headings in the ERT page for each flavor of ERT.
adds a section to the ERT page covering the paranormal ERTs.

unitystation / unitystation-wiki