added functionality to TwitchTVStream and TwitchTVAppGUI
    TwitchTVStream
	- getTitle() added
	- getGame() added
	- getViewers() added
	- getUrl() added
   TwitchTVAppGUI
	- added labels to show stream title, game, viewers and a link to the stream
fixed a bug, that occured, when a twitch stream was live and had no game set
added stream preview to TwitchTVAppGUI and getters for displayname and previewurls to TwitchTVStream