Simplify COM implementation traits

[kennykerr]

Currently, when implementing a COM method that accepts a COM interface as an input parameter you end up with a parameter that looks like this:

fn Method(&self, interface: &Option<IObject>);

This ends up being rather inconvenient because you necessarily have to convert the parameter from &Option<T> to Option<&T> via as_ref and then you need to check whether the option contains a value. With this change, the parameter looks like this:

fn Method(&self, interface: Option<&IObject>);

Naturally, a null parameter may still be passed by the caller but at least the as_ref is no longer required.