Contact authority for PoW difficulty

[BeaudanBrown]

We want to be able to have a DNS entry that snodes can ask for the current PoW difficulty
This would allow us to do things like hitting a "panic switch" to crank up the PoW difficulty if we detect that the network is being flooded

The storage server should poll (every 10 mins?) this authority and update a local difficulty value it uses to validate message PoW

If a message is received that has invalid PoW, the snode should respond with a 4XX specific for bad PoW difficulty and the correct difficulty value