Added hostname_resolve table
Added HostnameResolveMethod and ExpiryHostnameResolvesMinutes params.
Resolve includes mysql @@hostname at any case.
Support serializing/centralizing of database writes. Needed so as to
avoid too many concurrent writes which cause too many open connections
Added resolve, resolve_dao which handle hostname resolving
Activating serialized/centralized database writes on continuous
discovery
added "ExpiryHostnameResolvesMinutes" in config