Edit a lot of messages in the po file

The changes that Josh made to `words.py` have been reverted. It is now in the state that it was when we forked from Askbot.

I reached line 4798 of the PO file, or the start of the FAQ stuff. Some of my changes might be mis-formatted (e.g. have newlines where they shouldn't be). Eventually, someone should probably go through this file again and make sure it's correct.

I highly recommend using [Emacs' Po Mode](http://www.emacswiki.org/emacs/PoMode) to edit this file if you have no strong aversion to Emacs. It worked well for me, and prevents you making silly formatting mistakes.