Added Windows Audio Session API wrapper for WP8

This is the WinRT WP8 wrapper for the Windows Audio Session API that
will be used by Microsoft.Xna.Framework.Audio.Microphone to access raw
microphone data on the WP8 platform.
Updated version of the WP8 WASAPI wrapper.

Weeded out a timing bug, fixed the namespace and made sure that the
.winmd file is compiled with the correct filename.
Merge pull request #37 from Aztherion/master

Added the WinRT WP8 wrapper for audio capture through WASAPI