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
NO,
        /**
         * Optional arg that is a named argument and has a default value of
         * `null`. When possible, the default value should be specified.
         */
        OMITTED_NAMED_ARG,
        /**
         * Optional argument with default value omitted because they are
         * implicitly clear. That is, elements in an array or object may not
         * exist by default.
         * When possible, the default value should be specified.
         */
        OMITTED,
    };
    using Fallback = boost::variant<Optional,  std::string>;
    const std::string m_name; 
    const Type m_type;
    const std::vector<RPCArg> m_inner; 
    const Fallback m_fallback;
    const std::string m_description;
    const std::string m_oneline_description; 
    const std::vector<std::string> m_type_str; 
    RPCArg(