Showing line items on orders screen now when there are no shipments

Fixes #3958

Conflicts:
	backend/app/views/spree/admin/orders/_form.html.erb
fix for report locale names when extending via class_eval

* source issue: https://github.com/spree/spree/issues/4086
* try to maintain the reports not in a constant
* make it easier to add new reports over current merging arrays way
* clean up to avoid test breakage in the ui tests due to missing routes
* added a test on GET :index to check for regressions for my change

Fixes #4086
Fixes #4087