Report Exports - Add pre-calculated totals for non javascript templates

[Donatello-za]

We would like to export our reports to HTML and then send them via email but the Javascript based reports are causing issues. In order for custom plain HTML email templates to work we'll need to at the very least have the pre-calculated grand totals per category. The old project-hamster (+/- v2.91) used to have these totals but when the new templating was added around that time the total calculations were removed from the code.