node_queries.py

Task #9939: RA DB sql: replace drgXX bandwidth-to-storage matching by-name by such matching via extra resource groups (suggested by Adriaan). The type of such a resource_group is 'virtual'. This is essentially the same trick as done for 'node_group', so just rename that resource group type to 'virtual'. (We find removing a group type risky, so 'station_group' stays.)