Export inherited members of plugin classes

Plugin wrapper classes currently export only the members declared directly on the exported class. Public members inherited from .NET base classes are silently dropped from the Objo API surface, so wrapper class hierarchies — abstract plumbing bases with exported leaf classes, the standard shape for component sets — do not work: a method inherited by an exported class cannot be called from Objo. Exports should automatically include inherited public members, following C# member lookup through the exported type, so wrapper hierarchies work directly and only leaf classes need [ObjoExport].