New config (#6333)

* updated new-config to add trading_mode and margin_mode

* added trading_mode and margin_mode to config examples

* added okex config example

* new file:   config_examples/config_binance_futures.example.json

* removed trading_mode and margin_mode from base_config and binance and okex example

* deleted okex and futures config files

* updated full config file

* updated new-config command to add trading_mode and margin_mode to config

* new file:   config_examples/config_okex_futures.example.json

* removed config_okex_futures.example.json

* added trading_mode to test_start_new_config

* new-config asks exchange before asking futures

* Simplify trading_mode selection

* margin_mode is empty string for spot new configs

* build_config_commands sorted exchanges

* isort

Co-authored-by: Matthias <xmatthias@outlook.com>

freqtrade/exchange/okex.py

@@ -2,8 +2,9 @@ import logging
 from typing import Dict, List, Tuple
 
 from freqtrade.enums import MarginMode, TradingMode
-from freqtrade.exchange import Exchange
 from freqtrade.exceptions import OperationalException
+from freqtrade.exchange import Exchange
+
 
 logger = logging.getLogger(__name__)