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
Handle texture filter type "None" to force no mipmaps.
Update SoundEffect.cs
Update SoundEffectInstance.cs
Merge pull request #2458 from SickheadGames/PipelineTool

PipelineTool, Import XNA project
-16 is a more reasonable default.
Merge pull request #2459 from SickheadGames/nomip

Support Texture Filter None
Update NoAudioHardwareException.cs
Merge pull request #2457 from SickheadGames/Documentation

Audio Docs