added toModifications, to update the modifier directy
-> moving the logic of the attribute-style-setting to the attribute
swapped/renamed methods to access the DirectionUnitDependedAttribute
-attributes by index.
renamed: SideUnitDependendAttribute -> DirectionUnitDependentAttribute
moved logic from Siding into DirectionUnitDependentAttribute
removed Siding class
updated inheritance to DirectionUnitDependentAttribute