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>

tests/commands/test_build_config.py

@@ -44,6 +44,8 @@ def test_start_new_config(mocker, caplog, exchange):
         'fiat_display_currency': 'EUR',
         'timeframe': '15m',
         'dry_run': True,
+        'trading_mode': 'spot',
+        'margin_mode': '',
         'exchange_name': exchange,
         'exchange_key': 'sampleKey',
         'exchange_secret': 'Samplesecret',