Ticket 534 - RFE: Add SASL mappings fallback
    
    Bug Description:  If the mapping fails to find an entry the bind fails without
                      checking if other mappings would also match.
    
    Fix Description:  Added the fallback functionality.  Also added the ability to prioritize
                      the mapping order, and to be able to modify the mappings while
                      the server is up.
    
    https://fedorahosted.org/389/ticket/534
    
    Reviewed by: noriko & richm (Thanks!)