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
if (!desc->IsRange()) {
        range.first = 0;
        range.second = 0;
    }
    std::vector<CScript> ret;
    for (int i = range.first; i <= range.second; ++i) {
        std::vector<CScript> scripts;
        if (!desc->Expand(i, provider, scripts, provider)) {
            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("Cannot derive script without private keys: '%s'", desc_str));
        }
        std::move(scripts.begin(), scripts.end(), std::back_inserter(ret));
    }
    return ret;
}
UniValue GetServicesNames(ServiceFlags services)
{
    UniValue servicesNames(UniValue::VARR);
    if (services & NODE_NETWORK)
        servicesNames.push_back("NETWORK");
    if (services & NODE_GETUTXO)
        servicesNames.push_back("GETUTXO");
    if (services & NODE_BLOOM)
        servicesNames.push_back("BLOOM");
    if (services & NODE_WITNESS)
        servicesNames.push_back("WITNESS");
    if (services & NODE_NETWORK_LIMITED)
        servicesNames.push_back("NETWORK_LIMITED");
    return servicesNames;
}