Some small fixes and a GMless screen

I discovered some dead links in the hyperlinked PDF, so I fixed those and went through the whole file again, making small changes (mostly adding more ‘return to previous page’ links). I also pleased to introduce the official GMless screen (in both 8.5”x11” and A4 versions), so you can hide what you’re doing from prying eyes (even your own). It has all-new artwork on the outside and a lot of handy tables on the inside and can be folded in half to stand upright.