Improvement of PasscodeLockController- length of passcode 4 or 6, depending on user's respective ios version.

Improvement of PasscodeLockController- There was no option for users using iOS 9 and above to have a 6 characters passcode. That's a must have feature if it is available to use.

Now if a user is using below or iOS 9 then they can set 4 character long passcode as it was intend to. But users using iOS 9 above, will finally have the option to use 6 character long passcode.