Save and load processed data(such as alpha158) to avoid same processing every time

## 🌟 Feature Description
-Save processed data to file, and can load it for fitting to avoid reprocess the data every time.

## Motivation
- it needs to process the trading data every time, such as alpha158.
- User usually need to focus on algorithm optimization, but it processes the data every time and cost a lot of unnecessary time 

## Alternatives


## Additional Notes
