web: remove projects page and associated dingleberries

Alexander Strasser added a redirect on the web server, so this page is
no longer needed.

The current projects page is located on the wiki:
https://trac.ffmpeg.org/wiki/Projects

Signed-off-by: Lou Logan <lou@lrcd.com>
web/download: add FFmpeg 2.3.1

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>