Kraken: Fix Balances reporting 0 free (#1267)

* Kraken: Fix Balances reporting 0 Free

This switches to BalancesEx(tended) to get Held assets so we can
construct a Total, Held and Free.
Without this fix we get 0 balance from GetFree()
Haven't added tests because no construct for mocks and it's private
data. Considering adding mocks a bridge to far for this fix.

* Kraken: Simplify GetBalance

exchanges/kraken/kraken.go

@@ -494,25 +494,17 @@ func (k *Kraken) GetSpread(ctx context.Context, symbol currency.Pair) ([]Spread,
 }
 
 // GetBalance returns your balance associated with your keys
-func (k *Kraken) GetBalance(ctx context.Context) (map[string]float64, error) {
+func (k *Kraken) GetBalance(ctx context.Context) (map[string]Balance, error) {
 	var response struct {
-		Error  []string          `json:"error"`
-		Result map[string]string `json:"result"`
+		Error  []string           `json:"error"`
+		Result map[string]Balance `json:"result"`
 	}
 
 	if err := k.SendAuthenticatedHTTPRequest(ctx, exchange.RestSpot, krakenBalance, url.Values{}, &response); err != nil {
 		return nil, err
 	}
 
-	result := make(map[string]float64)
-	for curency, balance := range response.Result {
-		var err error
-		if result[curency], err = strconv.ParseFloat(balance, 64); err != nil {
-			return nil, err
-		}
-	}
-
-	return result, GetError(response.Error)
+	return response.Result, GetError(response.Error)
 }
 
 // GetWithdrawInfo gets withdrawal fees

exchanges/kraken/kraken_types.go

@@ -18,7 +18,7 @@ const (
 	krakenDepth            = "Depth"
 	krakenTrades           = "Trades"
 	krakenSpread           = "Spread"
-	krakenBalance          = "Balance"
+	krakenBalance          = "BalanceEx"
 	krakenTradeBalance     = "TradeBalance"
 	krakenOpenOrders       = "OpenOrders"
 	krakenClosedOrders     = "ClosedOrders"
@@ -204,6 +204,12 @@ type Spread struct {
 	Ask  float64
 }
 
+// Balance represents account asset balances
+type Balance struct {
+	Total float64 `json:"balance,string"`
+	Hold  float64 `json:"hold_trade,string"`
+}
+
 // TradeBalanceOptions type
 type TradeBalanceOptions struct {
 	Aclass string

exchanges/kraken/kraken_wrapper.go

@@ -613,7 +613,9 @@ func (k *Kraken) UpdateAccountInfo(ctx context.Context, assetType asset.Item) (a
 			}
 			balances = append(balances, account.Balance{
 				Currency: currency.NewCode(translatedCurrency),
-				Total:    bal[key],
+				Total:    bal[key].Total,
+				Hold:     bal[key].Hold,
+				Free:     bal[key].Total - bal[key].Hold,
 			})
 		}
 		info.Accounts = append(info.Accounts, account.SubAccount{