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
const std::map<std::string, UniValueType>& typesExpected,
    bool fAllowNull,
    bool fStrict)
{
    for (const auto& t : typesExpected) {
        const UniValue& v = find_value(o, t.first);
        if (!fAllowNull && v.isNull())
            throw JSONRPCError(RPC_TYPE_ERROR, strprintf("Missing %s", t.first));
        if (!(t.second.typeAny || v.type() == t.second.type || (fAllowNull && v.isNull()))) {
            std::string err = strprintf("Expected type %s for %s, got %s",
                uvTypeName(t.second.type), t.first, uvTypeName(v.type()));
            throw JSONRPCError(RPC_TYPE_ERROR, err);
        }
    }
    if (fStrict)
    {
        for (const std::string& k : o.getKeys())
        {
            if (typesExpected.count(k) == 0)
            {
                std::string err = strprintf("Unexpected key %s", k);
                throw JSONRPCError(RPC_TYPE_ERROR, err);
            }
        }
    }
}
CAmount AmountFromValue(const UniValue& value)