* 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>
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