Accept in memory data for backtest

[c0indev3l]

Hello,

A first step towart #237 could be (as discussed on Discord yesterday) to accept in memory data for backtests.
Currently we can pass a json dict of "symbol": {'open': [22, 22], 'high': [22, 22], ...} thats read as a .json file but we could input data as pure Python in memory data such a dict of dict of list (or numpy array).

Kind regards