This facilitates functionality required for [HIP-46](https://github.com/helium/HIP/blob/main/0046-lorawan-netid-routing.md)

[yoranom2]

This facilitates functionality required for HIP-46

• Supersedes PR 1285
• Create new chain var, routers_by_netid_to_oui that contains sorted list of tuples
• Each tuple associates a NetID to OUI for a roaming partner
• New functionality is primarily contained within State Channel client code

Originally posted by @dpezely in helium/blockchain-core#1412