[v6r11]  av-v6r11

I made 2 scripts:
- dirac-rss-query-resourcestatusdb.py (based on ResourceStatusClient): to query (select, insert, update, delete, add, modify) the ResourceStatusDB tables but I have tested it only for ServiceStatus and ServiceLog
- dirac-rss-query-downtimecache.py (based on ResourceManagemenetClient): to query (select, add, delete) the DownTimeCache table in the ResourceManagementDB

These should close https://github.com/DIRACGrid/DIRAC/issues/1597 and https://github.com/DIRACGrid/DIRAC/issues/1302