Redesign of the documentation overview page

["Jonathon Jongsma" <jonathon jongsma gmail com>]

It's been bugging me for a while (well, since the gtkmm.org redesign)
that the documentation overview page
(http://gtkmm.org/docs/gtkmm-2.4/docs/) doesn't match the rest of the
site.  So here's a proposal for a new overview page:
http://flickr.com/photo_zoom.gne?id=485784415&size=l

Sorry that the size of that image is a little small, hopefully you can
still read it.  I tried to keep the same basic layout as the existing
page, but using the new gtkmm.org header / sidebar to make it fit in
with the rest of the site.

I did make a few changes to the organization and content as well.  For
instance, I separated the 'tutorial' section and put it up top
prominently so that people coming to the site to learn about gtkmm
know to start there.  I also tried to put a note in the API reference
section to explain what we mean by "gtkmm 2.4".  I also removed some
items from the previous layout that would have duplicated stuff in the
main menu or sidebar links.

If anybody has comments, let me know.

--
jonner