The variable descriptive_names should work with inheritance #31

The function update_descriptive_names!(gui::GUI) should use the closest available supertype of the required field if available. E.g., if a new node is developed NewAbstracNonDisRES <: AbstractNonDisRES with the same fields as AbstractNonDisRES that should have the same descriptions of these fields, one should not be required to add description of these in the src/descriptive_names.yml file, instead it should look (if not present) for descriptions for supertypes.