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.

changed the description

@nicolas.cadart Can you have a look please ?

added 10 commits

• 5253c04c...536572d8 - 7 commits from branch master
• cef07c30 - [fix] Fix crash of "Is crash Analysing" option in stream mode
• 116a4be8 - [fix] Avoid warnings when save/Load LidarState in stream mode
• 63c0dd16 - [ui] display information messages to the user

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added 3 commits

• 38d3b883 - [fix] Fix crash of "Is crash Analysing" option in stream mode
• b243e49e - [fix] Avoid warnings when save/Load LidarState in stream mode
• 2d468988 - [ui] display information messages to the user

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approved this merge request

added 1 commit

• 500d7666 - [ui] display information messages to the user

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added 1 commit

• 985eb865 - [ui] display information messages to the user

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resolved all threads

merged

mentioned in commit a195089b