Version 5.1.7 Performance improvements in plot.py

[BennyThadikaran]

This version brings significant performance improvements in Plot.py execution.

Fast CSV file loads

In initial versions, the entire CSV file was being loaded only to use 160 to 250 lines of data. I wrote a function csv_loader to load the file in chunks and only load what is necessary. This provides about 40 to 70% load performance. See csv_loader execution times

Use of lru_cache

When switching to the previous or next charts in plot.py the resulting DataFrame and indicator data is cached using functools.lru_cache. Revisiting the same chart is now faster to load as you can see from the attached screenshot.