fixed issues with the App class which appeared due to bad commit before branching
updated the GetRootResult to search for/return MusicFolders and renamed the GetRootIndex method of the SubsonicService to GetMusicFolders
added the GetIndexResult class and the GetIndex method to the SubsonicService class
updated the IndexViewModel to inherit from the DetailViewModelBase class and the way it populates to use the info of a MusicFolder