Create detailed content for Sprint 4

[KetchCyork]

Also update overview schedule to link to the detail

[davebeach]

we need to be careful about spending time when in one sprint on future sprints. we really should not do that. A good example is sprint 2 - where users spent all this time going thorough and commenting on detailed prototype pages etc. This was done before we have reviewed it with them. Thus a lot of questions and comments were a bit premature (but useful). the rules of agile is a sprint is a sprint because you are only focused on that sprint and nothing else.