adds: new db fields and struct variables

- Intrduce DB update `channel` values: `feerate_base` and `feerate_ppm`
- Make fist use of now context realted DB migration
- Add `struct channel` members of the same name
- Use struct values instead of config when commiting new channels

lightningd/opening_control.c

@@ -223,7 +223,9 @@ wallet_commit_channel(struct lightningd *ld,
 			      true,
 			      &uc->local_basepoints,
 			      &uc->local_funding_pubkey,
-			      NULL);
+			      NULL,
+			      ld->config.fee_base,
+			      ld->config.fee_per_satoshi);
 
 	/* Now we finally put it in the database. */
 	wallet_channel_insert(ld->wallet, channel);