Launcher wizard: improve user experience

The launcher wizard that we implemented in 4.9.AM3 works but it lacks explanations that would help a novice user.
Suggested improvements:

• A novice user has no idea what a mission is all about. We should maybe add an explanatory label that tells the user what he's picking with a mission. And then we should explain what the mission that he has chose will provide.
  
• A novice user has no idea what the maven artifact elements are for.
  
• Generally speaking it is preferable to decorate missing input fields with a "*" than to mark them as errors (as one can see in most web forms). OpenShift tooling does this as a rule of thumb.
  
• Location is not decorated with an "required value" (or error) marker