[TIMOB-19010] Windows: Support Async methods on Native API wrappers

We currently "skip" any method that is Async on the native APIs right now. To properly support them will require generating a "Promise"-like wrapper. See https://msdn.microsoft.com/en-us/library/windows/apps/br211867.aspx Effectively we need to return an object that encapsulates the async operation and allows users to chain a series of async operations to run in series using callback methods. The important methods here are: then, done and cancel. Under the hood, we'll likely have to use ppltasks library to wrap up the async operations. See https://msdn.microsoft.com/en-us/library/windows/apps/hh780559.aspx