Avoid bad index errors on first visit to a registration commerce tab form on registration type.
Removing unused function registration_commerce_line_item_configuration -- just a reproduction of the same function in commerce.
Proper description for Administer Registration Commerce permission.
Building in logic to check for extant payment line items for a registration before adding to cart.
Stripping out rules version of cart uniqueness assertion (it has been coded into registration_commerce_pay_callback).
Misc coding style.
Installation hooks for adding the settings blob to registration type entities.
Altering forms to use entity settings blob rather than the old system variable.
Removed obsolete hook_entity_delete that was trying to fix the errors in our uniqueness rules execution.
Restructured settings logic to use registration_type settings field.
Comments, coding style, and messaging cleanup.