create handling fee adjustments from stock_locations

Conflicts:
	backend/app/controllers/spree/admin/stock_locations_controller.rb
	core/app/models/spree/item_adjustments.rb
	core/app/models/spree/shipment.rb
	core/app/models/spree/stock_location.rb
	frontend/app/views/spree/checkout/_summary.html.erb