[d20] Creatures can appear in inits twice

[Cory Dodt]

When a character rolls init twice, it shows up in the list twice. The [init] hook should check to see if a character is already in the list, and respond with an error message if the character already has init.

This is coupled with the solution to bug 003925, because a character with a legitimate reason to reroll init would need to first be removed from inits after this fix is in place. The only way to remove inits presently is using ".combat" which removes all of them.

[Cory Dodt (corydodt)]

Fixed this in vellumbot. See vellumbot.d20session.SortedRing