update the web version of FAQ and remove the texinfo version

[Yoshinori K. Okuji]

I updated the GNU GRUB FAQ on the web, because it was out of
date. It is still out of date in some respects, but I think they are
minor.

Also, I removed the appendix "FAQ" in the manual, as it was heavy to
sync two different versions. The reason why I chose the web version
was that this was easier to update (consider that the user wouldn't
update his/her installation very often).

BTW, I gave up the maintenance of the Japanese version of the web,
because it could waste my time a lot to keep it up to date with the
English version, and I don't think that was so useful to make GRUB
better. If someone is willing to take over the task, let me know.

Okuji