Some changes for website integration.

I ran a documentation build last night, so you can see the documentation at http://www.boost.org/doc/libs/develop/doc/html/align.html, but the redirect currently goes to the wrong place so http://www.boost.org/doc/libs/develop/libs/align/ doesn't work yet.

Also add a metadata file which will make it easier to add the library to the documentation list and keep it up to date.