Clean up Database Entries that are too old

The Lox distributor currently stores the lox_context indefinitely but the main reason for storing the lox_context in the first place is to keep the bridges received from rdsys in the correct place in the lox bridge table. Storing these values for a week is likely more than sufficient for this purpose. We've also discussed wanting to keep the context in case there is a need to roll back to some previous state and honour previously held credentials. It's still unclear whether or not such a scenario would occur in practice but it's possible that we may want to consider something like this if a certain type of bridge was blocked by protocol rather than through leaking of the bridge information. Then we may want to honour credentials that were spent during this blocking event.