Feature audio manager

Created an audio manager to handle loading and playing sounds throughout the app. A singleton class is used. Background music, menu buttons, pipe turning, clearing infection, and level complete sounds are implemented. Mini game sounds (spam/not spam correct buttons, bounce sounds) are not. Sounds for unveiling tiles and spreading infection are loaded but never called as our game doesn't track that over time.
Should these two `PDAudioManager` files exist? It looks to me like they're probably superseded by the `PipeDream/PDAudioManager` files and should be deleted.