Fix for issue #37 - Multiple SetUp Fixtures should be permitted on same ...

This should make it possible to use more than one SetUp fixture per namespace. The order they are executed in is not defined and depends on the implementation of the .NET Framework.

I think you need to comment what's happening in this block. That is, we already have found a SetUpFixture for the namespace and we are making this one a child of the first one found. I'm not really in love with this nesting, since the two are, in principle, of equal standing. But it can go in  this way and, if needed, be changed when we are doing the GUI.

More important... I'm worried about clearing the tests contained in the containing suite. Let's say we discover the first SetUpFixture and several contained fixtures. Then we discover the second SetUpFixture. Won't the contained fixtures be lost?