support creating IReference of any WinRT type

[tristanlabelle]

right now we have an internal implementation of IPropertyValue, which is not needed now that we have the handwritten PropertyValue class. the purpose of the IPropertyValueImpl was to provide IReference support, but that is unlikely to ever be used, especially since it doesn't work in the general case.

we should implement IReference for any WinRTStruct or WinRTEnum and once we do that, we can remove a lot of the code we have generated today and just use that