Currently the `getnetworkinfo` returns something like: 

```
"localservices": "0000000000000449",
```

Manually parsing this consistently gives me a headache (see also https://github.com/sipa/bitcoin-seeder/pull/77).

It would be useful to parse this and show the right combination of `NODE_NETWORK`, `NODE_GETUTXO`, `NODE_BLOOM`, `NODE_WITNESS`, `NODE_NETWORK_LIMITED` and `NODE_COMPACT_FILTERS`. In addition the help text for `getnetworkinfo` could be expanded to mention the right BIP numbers for known flags.

There is some ad hoc parsing to populate e.g. `localrelay`, etc (?).  Their help text could also refer back to `NODE_GETUTXO`.

See also: https://en.bitcoin.it/wiki/Protocol_documentation#Network_address
return res + "\"str\"";
    case Type::STR_HEX:
        return res + "\"hex\"";
    case Type::NUM:
        return res + "n";
    case Type::RANGE:
        return res + "n or [n,n]";
    case Type::AMOUNT:
        return res + "amount";
    case Type::BOOL:
        return res + "bool";
    case Type::ARR:
        res += "[";
        for (const auto& i : m_inner) {
            res += i.ToString(oneline) + ",";
        }
        return res + "...]";
    case Type::OBJ:
    case Type::OBJ_USER_KEYS:
        
        assert(false);
        
    }
    assert(false);
}
std::string RPCArg::ToString(const bool oneline) const
{
    if (oneline && !m_oneline_description.empty()) return m_oneline_description;
    switch (m_type) {
    case Type::STR_HEX: