828 allow room keys change and 827 password attributes to key

Passwords attributes changed to key attributes and now keys are only relevant to the user role, passwords are internal and created for when send_created is called.

refs #827
refs #828
You could have a single method `internal_password` to replace `internal_moderator_password` and `internal_attendee_password`. And it can be a private method.

ps: `unique_meetingid` is not private because it can possibly be used by the application that uses the gem. For the internal passwords I don't think we need this.