GUI: From selection descriptor 2

Roughness is a SelectionProperty now.

RoughnessItemCatalog and base class RoughnessItem for different roughness models are created.

Although there is only one roughness model now, in future the adding a new model will be easier.

Steps of SelectionProperty/Descriptor refactoring:

1. make SelectionProperty less generic, make catalogs usage mandatory, not optional
2. reduce usage of ad hoc SelectionDescriptors, e.g. descriptors that are not derived from SelectionProperty
3. move Descriptor functionality to Property
4. use Property instead of Descriptor
5. remove Descriptor from code
6. refactor serialization of Property

This MR is related to points 2.