Switch away from $this->data and start using new ways of displaying
content.
Set an empty terms to awoid warning when rendering.
Change the isolation level to public or the method will not display
Fix error handling to be done in the template.
Whitespace (I never learn...)
Theme for 2.0
Add to activity log, seems to be the thing to do these days.
I don't really understand when to return the view and when to set the
output, but I am sure there is a logic somewhere. Set output for these
two instead so we get some.
Update the mail template to work again.

Use local data, do not use Template() class (removed?). order_download
is gone, read up data from the order/order_to_download et al instead.