Task modules data saving

[sho-87]

Data saving should be moved to the individual task modules, rather than all being done in the main script. This would make it easier to keep tasks modular

Related to #2 and #3

[sho-87]

This is easy if saving CSV files, but currently all tasks write to the same Excel file. That already eliminates some modularity, as you'd need to create and pass in the Excel file/sheets to each task - unless the file is checked/opened at the head of each task but thats messy...