* 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
* Added volume controls in Example app
* Fixed occasional COMException when using Get- or SetSpotifyVolume
This exception only happens if Spotify is using an audio device different from the default one. Such a thing is only possible (as of v1.0.75.483.g7ff4a0dc) when using the "--enable-audio-graph" command line argument, that makes available the "Playback device" advanced option in Spotify.
