Additions

• Mega Stones can now be configured (in Showdown) to allow multiple valid users.
  • If the megaEvolves field is a "string", then it takes only that Pokemon.
  • If the megaEvolves field is a ["list", "of", "names"], then it takes any Pokemon in the list.
• Added item tags for form change items.

Bugfixes

• Regional forms can no longer use non-regional megastones (again).
  • This fix got reverted with the 1.7 update.
• Fixed rare Showdown crash.