send signal on item addition
update comments
More consistent and universal choice data handling
TODO
Only add choice data to line value when appropriate
Fix price display
Price calculation rework and misc refactoring
TODOS
startapp
Better name for variable. Also make less requests to db.
DRY and more readable code
Move common objects to mixin.

Also move choice_data_custom_size directly to context
consistently show selected options and product name
adjust columns for consistency
Make calculation results consistent with Oscar's basket totals calculation
Fix discrete pricing logic and rounding. Refactor
Do not add up line quantities
Handle discrete pricing scheme properly
optimize presentation
add indexes on quantity and min_order