Implement special notes for Uncanny Avengers

Figuring out exactly how many times Wolverine can overrun sounds
hard. For now, any subclass of VillainDeckSet can define a string (or an
array of strings) to display after "Additional Notes" in the
interface (note that right now, only notes from Villain/Adversary groups
are included in the response in SubmissionHandler).

Always leave a note.

[GH-15]