Homepage change

I've just released some changes to the layout of the site.  The home page is different; we're trying how things go if we sort by the top-level categories, if that helps people find things they're interested in more easily.

We have also added the ability to allow authors to 'feature' comment threads on their Instructables. You'll see a checkbox by the bottom of each top-level comment marked "Feature Comment".  Checking it will pull that comment and all its replies to the top of the comments, and keep them there (it will also close that thread to further replies so as not to be hijackable). We expect this to be used for threads that really add a lot to the Instructable, but which are in danger of becoming hidden on later comment pages as additional comments are made.  Use sparingly!  Also note that the rearrangement does require a page refresh; the thread won't pop to the top immediately.

There are a couple other small layout changes as well, nothing too big.  Also we've done a little work on contest management, which will help the admins do their work more easily but doesn't show for everyone else.