lightningd: save the fee_states into the database.

This is the final step: we pass the complete fee_states to and from
channeld.

Changelog-Fixed: "Bad commitment signature" closing channels when we sent back-to-back update_fee messages across multiple reconnects.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tools/generate-wire.py

@@ -221,6 +221,7 @@ class Type(FieldSet):
         'per_peer_state',
         'bitcoin_tx_output',
         'exclude_entry',
+        'fee_states',
     ]
 
     # Some BOLT types are re-typed based on their field name