Spotifywebapipython

* Added `PlayHistoryPage.GetTracks` method that gets a list of all tracks contained in the underlying `PlayHistory` list. This is a convenience method so one does not have to loop through the `PlayHistory` array of `Track` objects to get the list of tracks.

* Updated `TrackPageSaved` model to parse a `Track` object instead of a `TrackSimplified` object. The `Track` object contains the extra `Album`, `ExternalIds` and `Popularity` properties.
* Updated `TrackRecommendations` model to parse a `Track` object instead of a `TrackSimplified` object. The `Track` object contains the extra `Album`, `ExternalIds` and `Popularity` properties.
* Added `AlbumPageSaved.GetAlbums` method that gets a list of all albums contained in the underlying `Items` list. This is a convenience method so one does not have to loop through the `Items` array of `AlbumSaved` objects to get the list of albums.
* Added `TrackPageSaved.GetTracks` method that gets a list of all tracks contained in the underlying `Items` list. This is a convenience method so one does not have to loop through the `Items` array of `TrackSaved` objects to get the list of tracks.
* Added `EpisodePageSaved.GetEpisodes` method that gets a list of all episodes contained in the underlying `Items` list. This is a convenience method so one does not have to loop through the `Items` array of `EpisodeSaved` objects to get the list of episodes.
* Added `ShowPageSaved.GetShows` method that gets a list of all shows contained in the underlying `Items` list. This is a convenience method so one does not have to loop through the `Items` array of `ShowSaved` objects to get the list of shows.
* Added an `ImageUrl` property to all models that have an `Images` collection. The new property returns the first image url in the `Images` list, if images are defined; otherwise, null. This is a convenience method so one does not have to loop through the `Images` array of `ImageObject` objects to get an image url.

* Updated `SpotifyClient` methods to set the request header authorization key directly, rather than assigning a new dictionary to the value.
* Updated `SpotifyClient.MakeRequest` method to apply token refresh changes to the request authorization header if present. Prior to this fix, the request was still referencing the expired token value.
* Added `SpotifyAuthToken.HeaderKey` property for request header access.
* Added `SpotifyAuthToken.HeaderValue` property for request header access.
* Removed `SpotifyAuthToken.GetHeaders` method, as it was no longer required.

* Updated `SpotifyClient` to correctly support the `tokenUpdater` callable to update a token for an external provider.
* Updated `AuthClient` to correctly support the `tokenUpdater` callable to update a token for an external provider.

* Updated numerous classes with a `ToDictionary` method to allow dictionary representation of data.

* Updated `SpotifyClient` methods with better logging information.
* Updated `AuthClient` methods with better logging information.