Added documentation for classes in Microsoft.Xna.Framework.Audio
Doc updates for Microsoft.Xna.Framework.Audio.
Update AudioCategory.cs
Update InstancePlayLimitException.cs
Update NoAudioHardwareException.cs
Update SoundEffect.cs
Update SoundEffectInstance.cs
Update NoAudioHardwareException.cs
Merge pull request #2457 from SickheadGames/Documentation

Audio Docs