Improve consistency of addon's Python API

[donmccurdy]

Reported on Twitter, https://twitter.com/mcclure111/status/1233959819767427073, it seems that other I/O addons have some conventions on parameter naming that we've missed: export_selected should be ~~use_selected~~ use_selection , for one. We should fix that, and check if there are others that could be more consistent.

I think I would start with the FBX addon's naming as a guide, since its options and features are most similar to ours.

[donmccurdy]

Perhaps keeping the old export_selected supported for a few releases, with a warning, for backward compatibility.

[julienduroure]

I just created #957 to start the discussion, and how backward compatibility can be done

[donmccurdy]

I'd like to keep this open for now - ~~use_selected~~ use_selection is the reported property, but there are likely several others we could check consistent naming for.

[donmccurdy]

The options we want to match would be these: https://docs.blender.org/api/current/bpy.ops.export_scene.html. In general, we'd want use_* instead of export_*.

[julienduroure]

Is there still some cases we need to rename here?

[julienduroure]

Seems we can close this now