Train Rare and Epic Heroes to become Legendary

This should be a nice addition to the HA for F2P folks. Maybe I’d not feel too bad pulling a Bane using my hard-earned token knowing I could transform him into a 5* later on.

I don’t suggest upgrading their specials, but only better stats once they’ve transformed into a higher star. And I don’t suggest this applies to any 5* either (no need for 6* heroes ffs).