Fix crash analysis and save load reaction

1. Display information messages to the user :

• An instruction message
• If an empty json file is saved.
• If there is no property to display (if the json file loaded is empty for exemple)

2. Avoid warnings when save/Load LidarState in stream mode
   The properties Start and Stop of the Stream are "vtkSMProperty".
   Casting it into a proxy property raises a warnings that can be confusing for the user.

3. Fix crash of "Is crash Analysing" option in stream mode
   During "CrashAnalysing" option:
   If the directory can not be created boost::filesystem raises an error and the application crash.
   We add a try{} catch{} to avoid that.