Read from pg_roles as only superusers can read pg_authid

Contents is same except password is masked. Password does not seem very important to view as it is encrypted anyway.

Close #53

pglablib/catalog/PgAuthIdContainer.cpp

@@ -10,7 +10,7 @@ std::string PgAuthIdContainer::getLoadQuery() const
 		result += ", rolbypassrls";
 
 	result += "\n"
-		   "FROM pg_authid";
+		   "FROM pg_roles";
 	return result;
 }