The plugin objects are MarshalByRefObject stubs, which means they
don't actually implement the interfaces we're checking for. There's
some additional overhead to do the interface check. We can avoid
it by doing the interface queries during initialization, and just
checking some bit flags later on.
Also, in the extension script info window, show a list of
implemented interfaces.
Updated the RuntimeData directory finder to work, and made the
stuff that crashed when the directory wasn't found crash in less
obvious ways. Under Mono+Linux it still falls over with some
complaints about ListViews. This will need some work.
