Require current password when using passwd to change your own password.
    
    Add a new required parameter, current_password. In order to ask this
    first I added a new parameter option, sortorder. The lower the value the
    earlier it will be prompted for.
    
    I also changed the way autofill works. It will attempt to get the default
    and if it doesn't get anything will continue prompting interactively.
    
    Since current_password is required I'm passing a magic value that
    means changing someone else's password. We need to pass something
    since current_password is required.
    
    The python-ldap passwd command doesn't seem to use the old password at
    all so I do a simple bind to validate it.
    
    https://fedorahosted.org/freeipa/ticket/1808