Try to implement IClosable that maps to System.IDisposable in .Net (WIP)

[forderud]

GOAL: Try to implement the WinRT IClosable interface that is automatically mapped to IDisposable in .Net code.

.Net interop doc: https://github.com/microsoft/CsWinRT/blob/master/docs/interop.md

Build warnings:

>TlbImp : warning TI3015: At least one of the arguments for 'MyInterfaces.IInspectable.GetIids' cannot be marshaled by the runtime marshaler.  Such arguments will therefore be passed as a pointer and may require unsafe code to manipulate.
>TlbImp : warning TI3015: At least one of the arguments for 'MyInterfaces.IClosable.GetIids' cannot be marshaled by the runtime marshaler.  Such arguments will therefore be passed as a pointer and may require unsafe code to manipulate.
>TlbImp : warning TI3015: At least one of the arguments for 'MyInterfaces.MyServerClass.GetIids' cannot be marshaled by the runtime marshaler.  Such arguments will therefore be passed as a pointer and may require unsafe code to manipulate.

Open questions

• Does TlbImp support WinRT interfaces inheriting IInspectable?
• Is it possible to use WinRT interfaces in "legacy" COM?