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
{
public:
    RPCHelpMan(std::string name, std::string description, std::vector<RPCArg> args, RPCResults results, RPCExamples examples);
    std::string ToString() const;
    
    bool IsValidNumArgs(size_t num_args) const;
    /**
     * Check if the given request is valid according to this command or if
     * the user is asking for help information, and throw help when appropriate.
     */
    inline void Check(const JSONRPCRequest& request) const {
        if (request.fHelp || !IsValidNumArgs(request.params.size())) {
            throw std::runtime_error(ToString());
        }
    }
private:
    const std::string m_name;
    const std::string m_description;
    const std::vector<RPCArg> m_args;
    const RPCResults m_results;
    const RPCExamples m_examples;
};
#endif