Initial (totally borked commit, I'm sure, but hey, it compiles!) commit of FileMedia object.

This contains the beginnings of the FileMedia object. With this, it should be theoretically possible to record some media and play it back.

Things to do in it:

I'm not using talk_base::scoped_refptr because most of the cricket namespaced objects don't have Release or other such functions.

Thoughts, comments, telling me why this is terrible and I should never do C++ again, etc. would be great.