Added castor::exception::InvalidConfiguration in order to work towards

addressing the following RFE:

bug #67945: RFE: The mighunter should not start if the migration and stream policy modules are not configured properly

Note that this particular commit updated the manual page for serrno.h to includethe new  constant SEINVALIDCONFIG.

mediachanger/castorrmc/h/serrno.man

@@ -181,6 +181,9 @@ The following error values might be returned by any package:
 .TP
 .B SENOVALUE
 (1042) No value
+.TP
+.B SEINVALIDCONFIG
+(1043) Invalid configuration
 
 .SH COPYTAPE ERRORS
 None yet