added a new config parameter that allows disabling honoring key expiry.

We use redis to store raw, unaggregated data in our database.
The database is snapshotted every night before aggregation, and kept for 30 days. So the algorithm can be re-run on old data if a bug is discovered in the algorithm.

When loading old dumps we encountered the problem that the ttls of those keys have already expired, and we ended up with an empty database.
This parameter option allows one to disable ttl checking in these cases.