Option to trash old team-ups when earning new one

Unknown

This has happened too many times:

1. Fights grueling battle against high level opponents
2. Victory!
3. Finds out team-up storage was full with useless powers
4. Sadface

If a player's team-up storage is full, why not allow them to trash an old team-up when they earn a new one? Team-ups are hard to track right now since you can only see your stored team-ups during the battle preview screen, so this would be a big convenience for players.