[OPENENGSB-1678] updated the documentation how the changing of the backend database have to be done (property placeholder)
[OPENENGSB-1678] updated the documentation how the changing of the backend database have to be done (property placeholder)

openengsb/openengsb,openengsb/openengsb,openengsb/openengsb,openengsb/openengsb,openengsb/openengsb,openengsb/openengsb