Improving coverage

Improve coverage and testing rework

This rework the testing framework by removing the need for F3D_GEN_REF and using output option instead.

This add many verbosity test to improve coverage This adds a few missing tests

Considered classes

• AnimationManager
• Loader
• OffscreenRender
• GenericImporter
• MetaReader
• PostProcessFilter
• vtkF3DRenderer*

The following classes will require more work:

• F3DOptions will require a --config option
• F3DAnimationManager will require interactions
• vtkF3DInteractorStyle will require interactions
• remaining part of vtkF3DRenderer* will require interactions
• Mapper/Render classes: Please take the lead on these classes @michael.migliore

Up to 73.5%.

related to #99 (closed)

This also rework the testing framework