Provide method to aggregate tickets into a single file per order.
Switch to a new system of recording files linked to tickets.
Removed Features field definitions.
Removed file deletion code from drush command.
Move file access hook implementations into PDF submodule.
pdf: Track files by entity ID and entity type, not just 'scope'.
Standardise command for generating tickets for order, line item, or ticket entities.
Clean-up.
Add 'completed' to the default valid order statuses.