* Draft: allow objects in layers to have overrides
Fixes#17844.
1. When an object is put in a layer it always adopts the properties of that layer.
2. Properties of the object that are subsequently changed are considered overrides.
3. When the properties of the layer, or the object in the layer, are then changed so that they match again, there is no longer an override, and properties are synced again.
4. The layer and the layer container object get an extra Tree view context menu option "Reassign properties of layer"/"Reassign properties of all layers".
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