Add shipping cost as separate value

Problem/Motivation

Currently it doesn't seem possible to get the order sum without shipping cost, which is important for reports in many cases.

It would be great to either have the order sum without shipping costs or have the shipping costs as separate field available so it can be subtracted from the order sum for example by using views_simple_math_field

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes