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
extern uint256 ParseHashV(const UniValue& v, std::string strName);
extern uint256 ParseHashO(const UniValue& o, std::string strKey);
extern std::vector<unsigned char> ParseHexV(const UniValue& v, std::string strName);
extern std::vector<unsigned char> ParseHexO(const UniValue& o, std::string strKey);
extern CAmount AmountFromValue(const UniValue& value);
extern std::string HelpExampleCli(const std::string& methodname, const std::string& args);
extern std::string HelpExampleRpc(const std::string& methodname, const std::string& args);
CPubKey HexToPubKey(const std::string& hex_in);
CPubKey AddrToPubKey(FillableSigningProvider* const keystore, const std::string& addr_in);
CTxDestination AddAndGetMultisigDestination(const int required, const std::vector<CPubKey>& pubkeys, OutputType type, FillableSigningProvider& keystore, CScript& script_out);
UniValue DescribeAddress(const CTxDestination& dest);
unsigned int ParseConfirmTarget(const UniValue& value, unsigned int max_target);
RPCErrorCode RPCErrorFromTransactionError(TransactionError terr);
UniValue JSONRPCTransactionError(TransactionError terr, const std::string& err_string = "");
std::pair<int64_t, int64_t> ParseDescriptorRange(const UniValue& value);
std::vector<CScript> EvalDescriptorStringOrObject(const UniValue& scanobject, FlatSigningProvider& provider);
UniValue GetServicesNames(ServiceFlags services);
struct RPCArg {
    enum class Type {
        OBJ,
        ARR,
        STR,
        NUM,
        BOOL,
        OBJ_USER_KEYS, 
        AMOUNT,        
        STR_HEX,       
        RANGE,         
    };
    enum class Optional {