refine URLs

[bluesomewhere]

eg, a lot of the /attend/blah links don't need /attend/ in them. set up redirects, though, don't delete any existing URLs.

... and make sure to take notes for next year's website so I can get it right the first time.

[bluesomewhere]

good enough for this year. will take this year's site and work backwards to build URL scheme for next year's site.