Object editor should handle generic types

[bleroy]

Currently, if you pick a generic type, we throw an argument exception.

[ermau]

The trick here is our type interface has no generic information so the best we could do is look for `n to filter them out. The reality is though that this was overlooked and it's actually valid to be able to select a generic type here, the trick is we'd need a way of selecting the type arguments.

In the interim it's my suggestion that the platform temporarily self-filter out generics.