* Create ProxyConfig class + Unit tests
* Use ProxyConfig in SpotifyLocalAPI
* Refactor WebProxy creation in ProxyConfig
* Use ProxyConfig in SpotifyWebAPI
* Add ProxyConfig parameter in GetAlbumArt methods
* Add ProxyConfig to WebAPIFactory
* Add proxy settings to Example app
* Fix ArgumentNullException in GetAlbumArtUrl when not using proxy
* Performed requested changes
- Removed redundant "this".
- Added necessary null checks.
- Added a ProxyConfig property to SpotifyLocalAPIConfig and removed constructor overloads with it in SpotifyLocalAPI and RemoteHandler.
* Updated Example app
sealed StringAttribute because it is only contains text as attribute
sealed SpotifyWebAPI class as it implements IDisposable
Changed Exception catching where the Exception is not used to ignore the Exception object
Removed Console.WriteLine("Exception: " + e.Message) int HttpProcessor.Process as it is a library function which might not be used in a console application
