Simplify/correct. More commits to follow.

First of a few commits to simplify and correct.

Delete paragraph about how to get added to this directory. (It's now dead simple and implicit: edit this page as you see fit.)

Make all links go directly to projects. This eliminates some 404s, eliminates links to other pages on this site (which are mostly incorrect anyway).

Fix inaccuracies in descriptions I'm aware of.

Add questhub.org entry.

Delete yapc entry.