(from discussion on IRC. Currently a global `settxfee` has to be changed to override the fee rate, it would make sense to be able to specify it on a per-transaction basis. This would continue #7518)

```
-*- jonasschnelli thinks we should probably add a optional feerate parameter to fundrawtransaction
<wumpus> jonasschnelli: there isn't one yet?
-*- jonasschnelli looking..
<wumpus> I'm surprised, would be so much better than changing a global
<jonasschnelli> no.. i don't think so. Maybe there is a PR.
<sipa> there is a pr
<jonasschnelli> Hard to keep track of everything. :)
<wumpus> no, the PR does it wrong
```

Regarding implementation:

```
<jonasschnelli> The ugly thing is, that CreateTransaction uses the static DEFAULT_TARGET
<wumpus> passing in an optional feerate would be the obvious thing to do
<jonasschnelli> So, this would require some refactoring.
<sipa> just add a confirmation target to coincontrol
<jonasschnelli> Yes. This sounds good.
<wumpus> right, just slap it into coincontrol
<sipa> wasn't there a PR that added a bunch of options to fundrawtransaction?
<sipa> including that
<jonasschnelli> Not the feerate.
<jonasschnelli> But the rest is merged.
```

+ HelpExampleCli("walletpassphrase", "\"mypassphrase\" 30") +
            "\nCreate the signature\n"
            + HelpExampleCli("signmessage", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XZ\" \"my message\"") +
            "\nVerify the signature\n"
            + HelpExampleCli("verifymessage", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XZ\" \"signature\" \"my message\"") +
            "\nAs json rpc\n"
            + HelpExampleRpc("signmessage", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XZ\", \"my message\"")
        );
    LOCK2(cs_main, pwalletMain->cs_wallet);
    EnsureWalletIsUnlocked();
    string strAddress = params[0].get_str();
    string strMessage = params[1].get_str();
    CBitcoinAddress addr(strAddress);
    if (!addr.IsValid())
        throw JSONRPCError(RPC_TYPE_ERROR, "Invalid address");
    CKeyID keyID;
    if (!addr.GetKeyID(keyID))
        throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to key");
    CKey key;
    if (!pwalletMain->GetKey(keyID, key))
        throw JSONRPCError(RPC_WALLET_ERROR, "Private key not available");
    CHashWriter ss(SER_GETHASH, 0);
    ss << strMessageMagic;
    ss << strMessage;
    vector<unsigned char> vchSig;
    if (!key.SignCompact(ss.GetHash(), vchSig))
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Sign failed");
    return EncodeBase64(&vchSig[0], vchSig.size());
}
UniValue getreceivedbyaddress(const UniValue& params, bool fHelp)