Update cap_msmf.cpp

Fixed bugs and completed the change.  I believe the new classes need to be moved to a header file as the file has become to large and more classes need to be added for handling all the asynchronous problems (one wrapping IAsyncAction in a task and another for making a task out of IAsyncAction).  Unfortunately, blocking on the UI thread is not an option in WinRT so a synchronous architecture is considered "illegal" by Microsoft's standards even if implementable (C++/CX ppltasks library throws errors if you try it).  Worse, either by design or a bug in the MF MediaCapture class with Custom Sinks causes a crash if stop/start previewing without reinitializing (spPreferredPreviewMediaType is fatally nulled).  After decompiling Windows.Media.dll, I worked around this in my own projects by using an activate-able custom sink ID which strangely assigns 1 to this pointer allowing it to be reinitialized in what can only be described as a hack by Microsoft.  This would add additional overhead to the project to implement especially for static libraries as it requires IDL/DLL exporting followed by manifest declaration.  Better to document that it is not supported.

Furthermore, an additional class for IMFAttributes should be implemented to make clean architecture for passing around attributes as opposed to directly calling non-COM interface calls on the objects and making use of SetProperties which would also be a set up for an object that uses the RuntimeClass activation ID.

The remaining changes are not difficult and will be complete soon along with debug tracing messages.