Reorganized the UserGuide

There is a lot of information in the user guide. This pull request is an effort to structure this information a little more.

 * The wiki content is tailored a lot towards Fit, although Slim is the prefered test system
 * More hierarchy, instead of everything on the same level (although it had some advantages too)
 * Sections to get you started with wiki and acceptance tests. Wiki is useful for non-techies, whereas writing acceptance tests is a development effort.