a few minor doc tweaks

fix link to website from guide, and mention svn commands
Wow that sed command makes my head spin. Assuming that ! after a / / pair means invert the condition, then that looks feasible to me, but I hope it has been tested!

There is an argument that people should be looking *very* *carefully* at deletions as it means that we're potentially breaking external links/bookmarks. While I'm not too bothered about /v/latest, I'd suggest adding a warning here about deleting files from the main website - not a complete ban necessarily, but "proceed with care".