Improve Importers Progress Management

[mwestphal]

Context
F3D can display a progress bar when loading a file, however, F3D relies on the progress reporting done by the readers and importers. Some of readers and importers we use, either from F3D or VTK, do not report accurate progress or progress at all.

The idea os this issue is to investigate the status of the different importers and readers in regards to progress reporting, and improve the one that do a bad job of it. First in F3D and second in VTK directly.

Suggested solution

• Investigate each and every readers and importers in use and check that they perform progress reporting.
• For the one that don't, implement a simple progress reporting mechanism and merge it into F3D and VTK

Skills needed

• Knowing how to contribute to VTK is a plus

Notes

• OBJ importer does not have progress
• glTF importer does not have progress
• Other importers may not have progress either

[mwestphal]

Good first issue for a VTK developer

[mwestphal]

glTF does not have progress either