Changing materials deletes secondary and tertiary materials

When a building with multiple materials is constructed, and then the material is changed afterwards, the order for reconstruction is always given with the last selected element.

In Reconstructable.RequestReconstruct, there is a hard assumption of only one element per building type, and the secondary material is lost when the new building is placed. In reality, the UI allows for up to 3 elements per buildings (some mods utilize this, please don't assume only 2 either! This limitation is found in MaterialSelectionPanel.OnPrefabInit)