Cache DNS to storage for offline use

[RangerMauve]

• Either add persistence logic via dns-query or over the built in storage
• In-Memory cache for domains
• Fetch from In-Memory before TTL
• Fetch from In-Memory on query fail
• Periodically save In-Memory cache to storage
• Persist cache on close
• Attempt to load cache from storage on load

Is there a way we can reshare records between peers longer term?

[RangerMauve]

We might also want to replace this with using the OS's DNS resolution so that people can add to their hosts file or use the DNS from their network provider (this is important for some funky mesh network stuff I want to do)