Geometry_Engine: SetGeometry for Grid objects should project curve to XY plane

#### Description:

Currently all `Create.Grid()` methods project the grid curve to the XY plane. Therefore, it stands to reason that the `Modify.SetGeometry(Grid)` method should as well.

If for some reason one wishes to have grid curves outside of the XY plane, the auto-generated Create method can do that, as can SetProperty, as they use the default setter which does not project. But this seems like a very niche use case.