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
std::string ToString(bool oneline) const;
    /**
     * Return the type string of the argument when it is in an object (dict).
     * Set oneline to get the oneline representation (less whitespace)
     */
    std::string ToStringObj(bool oneline) const;
    /**
     * Return the description string, including the argument type and whether
     * the argument is required.
     */
    std::string ToDescriptionString() const;
};
struct RPCResult {
    const std::string m_cond;
    const std::string m_result;
    explicit RPCResult(std::string result)
        : m_cond{}, m_result{std::move(result)}
    {
        assert(!m_result.empty());
    }
    RPCResult(std::string cond, std::string result)
        : m_cond{std::move(cond)}, m_result{std::move(result)}
    {
        assert(!m_cond.empty());
        assert(!m_result.empty());
    }
};
struct RPCResults {
    const std::vector<RPCResult> m_results;
    RPCResults()