Doc review

Here are some documentation enhancements, IMHO.

Also, I would like to talk about these points
* "load test" VS "stress test": we should choose, it's confusing when going from one to an other all over the doc.
* index.rst VS introduction.rst: it seems to me that there is some sort of two "intro" with some repetitions.
* Quickstart: the page is *so* huge that it gets sacry if that's the *quick* start. What about splitting this so that we have a proper "Quickstart" and a "Going further" on it's own ?