Updated Quick Start and Usage docs

[Sébastien Pierre]

Hi all,

Here are the updated version of the quick start and usage docs (thanks a
lot Sanjoy and Bryan for your detailed comments !). I took into account
everything that was suggested.

I also tried to rework the quick start schema (upper-left) according to
Bryan's suggestions, but am still unsatisfied with it. I think it is
difficult to "say it all", as I tried to present things from a
centralized point of view i the first place.

The problem is that I really started this schema as an illustration of
the particular Mercurial setup we use in our team, and that I did not
really think about the "general" case.

So, suggestions and alternative schema and description texts are
welcome :)

Taking into account some comments on the colors, you will also find
alternative colouring for the documents, so I would be glad to hear
which colour you prefer.

The docs are now exported to Firefox-savvy SVG, so that you can view and
print them in vector format (no more bitmap problems) -- you can also
edit them with Inkscape (or Illustrator).

Everything is available here: http://people.type-z.org/seb/mercurial/

Thanks again for the feedback :)

 -- Sébastien