Blender Git Loki

Fix object assets getting duplicated after dropping

The operator run when dropping objects would duplicate the dropped object and
place that in the scene, even though that was just appended. Addressed by
making the duplication optional for the operator. If the duplication is not
requested, the object is just added to the scene (if needed), repositioned
based on the drop location and selected (deselecting other objects).
This makes the operator work as expected when using it to drop assets.

Reviewed as part of https://developer.blender.org/D11536.

Reviewed by: Bastien Montagne