main doc HTML page changed

[Graham Percival]

I've updated the main page of the docs.  I tried to give more prominence 
to the glossary and the examples/snippets, and tried to hide the 
regression tests (not that any non-developer looks at them anyway...). 
Users should be looking at the tutorial, glossary (if applicable), the 
manual, and the snippets.  Maybe the examples as well.


I'm not religiously convinced that the new design is perfect, and for 
some reason HTML pages tend to attract a lot of opinions, so if you have 
any suggestions, go ahead.  I'm open to changing it.

Note that this is only in GIT right now.

Cheers,
- Graham