auto populate features based on a prepended % in the strategy (remove feature assignment from config). Update doc/constants/example strategy to reflect change

config_examples/config_freqai.example.json

@@ -56,20 +56,9 @@
         ],
         "train_period": 30,
         "backtest_period": 7,
-        "identifier": "new_corrlist",
+        "identifier": "example",
         "live_trained_timerange": "20220330-20220429",
         "live_full_backtestrange": "20220302-20220501",
-        "base_features": [
-            "rsi",
-            "close_over_20sma",
-            "relative_volume",
-            "bb_width",
-            "mfi",
-            "roc",
-            "pct-change",
-            "adx",
-            "macd"
-        ],
         "corr_pairlist": [
             "BTC/USDT",
             "ETH/USDT",