Market price info retrieval

[JustForDev2020]

New function added in 'balance.py' to retrieve info about trading pair:

• Specific: return one minute candlestick data for the selected date
• Range: returns candlesticks for a time range, with a custom interval

Important to input date/time as 'dd/mm/yyyy hh:mm:ss' to avoid exceptions or wrong data (not error handled)