More UI improvements for commercial advertisements

- Bolder text in commercial advertisement image.
- Validate like and dislike menu items to false if now playing is an ad.
- Use the commercial advertisement image in the history view.
- Clean up Song.h & Song.m to use dictionary literal and formatted to look aesthetically pleasing.
- Cache the now playing song’s advertisement status in the song’s object, only checking if the NSNumber (advertisement) is nil. This is used for HistoryItem and HistoryController stuff.