Add C++/WinRT Windows Runtime Component

[michael-hawker]

It'd be good to add an additional Windows Runtime Component to the project, but in C++.

This can be then used to have common data types that can be shared between the C# WRC and the C++ App itself.

Part of this could be an example of how to have a common data structure which can be populated in the app, modified by the C# WRC as part of an operation for a control, and then re-read back within the C++ app layer.

e.g. Having the C++ app select an image, using the Image Cropper control in the Toolkit to crop that image, and passing the resulting stream back to the C++ app...

[michael-hawker]

Another example could be showing how a data source in the C++ WRC (like a list/observablecollection of items) can be displayed within a component in the Toolkit but still manipulated by other code in the app or C++ WRC.