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
"    \"reachable\": true|false,             (boolean) is the network reachable?\n"
            "    \"proxy\": \"host:port\"               (string) the proxy that is used for this network, or empty if none\n"
            "    \"proxy_randomize_credentials\": true|false,  (string) Whether randomized credentials are used\n"
            "  }\n"
            "  ,...\n"
            "  ],\n"
            "  \"relayfee\": x.xxxxxxxx,                (numeric) minimum relay fee for transactions in " + CURRENCY_UNIT + "/kB\n"
            "  \"incrementalfee\": x.xxxxxxxx,          (numeric) minimum fee increment for mempool limiting or BIP 125 replacement in " + CURRENCY_UNIT + "/kB\n"
            "  \"localaddresses\": [                    (array) list of local addresses\n"
            "  {\n"
            "    \"address\": \"xxxx\",                 (string) network address\n"
            "    \"port\": xxx,                         (numeric) network port\n"
            "    \"score\": xxx                         (numeric) relative score\n"
            "  }\n"
            "  ,...\n"
            "  ]\n"
            "  \"warnings\": \"...\"                    (string) any network and blockchain warnings\n"
            "}\n"
                },
                RPCExamples{
                    HelpExampleCli("getnetworkinfo", "")
            + HelpExampleRpc("getnetworkinfo", "")
                },
            }.Check(request);
    LOCK(cs_main);
    UniValue obj(UniValue::VOBJ);
    obj.pushKV("version",       CLIENT_VERSION);
    obj.pushKV("subversion",    strSubVersion);
    obj.pushKV("protocolversion",PROTOCOL_VERSION);
    if (g_connman) {