new website (general info)

[Graham Percival]

In the hopes of convincing Han-Wen that we should include the
website in the main branch, I've done my first pass at rearranging
it.  You can see it in the web-gop/ branch (cd texinfo && make),
or here:

http://percival-music.ca/blogfiles/lilypond-general.pdf
http://percival-music.ca/blogfiles/out/lilypond-general_toc.html#SEC_Contents

Things to note:
- yes, it's in pdf as well.
- I'm calling it "general info" rather than "website" in an
  attempt to reinforce that fact.
- I'm doing the overall structure here.  (think of Sep 2007, when
  GDP was doing the high-level organization)
- I split the stable docs+downloads away from the unstable
  docs+downloads.  I did this yesterday (before Jan discovered
  the Dec 2008 release policy), but this helps to explain my
  position there as well.  :)
- we have warnings about reading the Crash course before people
  download stuff.
- the Documentation/index.html file will be removed; links to the
  manuals come directly from the general info pdf/html/info files.

Cheers,
- Graham