The "feefilter" p2p message is used to inform other nodes of your mempool min fee which is the feerate that any new transaction must meet to be accepted to your mempool. This will allow them to filter invs to you according to this feerate.
Creates the generatetoaddress rpc which is virtually identical to the generate rpc except that it takes an argument for the address to mine to. It does not rely on wallet functionality.
The mining code shared by generate and generatetoaddress has been moved to another method to reduce duplication.