Save as images, other features and fixes

[BennyThadikaran]

New Feature: Save charts as images to file - cafb24983394

• added --save argument option
• added SAVE_FOLDER option in config
• added help on first run.

New Feature: Only plot new detected patterns - f2f89f99998

• Maintain all active patterns in market in state folder.
• Removes patterns no longer active in market

New Feature: On chart, jump to any index in chart with j - c693b2a5ea

Load & plot charts from json files in state folder - 4bd8050d0ec

• Log helpful messages on --plot option usage

Fix: No patterns for missing dates when using --date option - 51f19b65e3

• get previous candle in case of holidays, weekends, missing days
• Remove weekend warnings and WEEKEND_WARN config option

Fix: handle empty csv files - 2a01e36432

Consistent naming for all definitions - snake case - dccdf05b78f

Minor code formatting - d18bf9fec1f