CommandBucket should determine argument types by method parameters

[tyler569]

I envision being able to write /tp as

@Command("tp")
void teleportLocation(Player sender, Vector3 target) {
    sender.teleport(target)
}

@Command("tp")
void teleportPlayer(Player sender, Player target) {
    sender.teleport(target.location())
}

And have CommandBucket figure everything else out - it should see they collapse to children of "tp", it should see that the Vector3 is a "minecraft:vec3", and that the Player is a "minecraft:entity" the the scoping flags to be only a single player.

It should also parse the string arguments internally, so the Command methods don't need to re-do the same parsing work.