fix help strings shown to the user

freqtrade/constants.py

@@ -4,6 +4,7 @@
 bot constants
 """
 DEFAULT_CONFIG = 'config.json'
+DEFAULT_EXCHANGE = 'bittrex'
 DYNAMIC_WHITELIST = 20  # pairs
 PROCESS_THROTTLE_SECS = 5  # sec
 DEFAULT_TICKER_INTERVAL = 5  # min
@@ -21,6 +22,7 @@ ORDERTYPE_POSSIBILITIES = ['limit', 'market']
 ORDERTIF_POSSIBILITIES = ['gtc', 'fok', 'ioc']
 AVAILABLE_PAIRLISTS = ['StaticPairList', 'VolumePairList']
 DRY_RUN_WALLET = 999.9
+DEFAULT_DOWNLOAD_TICKER_INTERVALS = '1m 5m'
 
 TICKER_INTERVALS = [
     '1m', '3m', '5m', '15m', '30m',