Assimp format (fbx, dae, ...) provide empty metadata

[mwestphal]

Describe the bug
F3D support many formats through the assimp plugin, however the meta data provided for these formats is empty

To Reproduce
Steps to reproduce the behavior:

1. Open the file using f3d --no-config -m 16bit.fbx

Expected behavior
Meta data should contain information

System Information:

• OS: Any
• GPU and GPU driver: Ant

F3D Information
Paste the content of f3d --version: 3.0.0

Additional context
F3D uses vtkF3DMetaImporter::GetMetaDataDescription() to recover that information, something must be going wrong there.

[mwestphal]

Point sprites also do not work with assimp, I think this is related.