Update cap_msmf.cpp

Added WinRT MF capture support using MediaCapture and a custom sink, while removing offending references to device enumeration and the sample grabber sink which are implemented through the latter.  This change is for initial support, a decision must be made on how to bind the additional interfaces as when dealing with video files, the old code and interfaces are all valid.

The sink is designed for non-WinRT support not for compatibility with older versions of Windows as all of the interfaces require a minimum of Windows Vista.  Yet the custom sink offers potentially more flexibility into the future and perhaps a faster implementation and could easily be selectable via a setting parameter.