Description

Small changes to the NLCC stress

Correct a minus sign wrong in the NLCC force in the previous commit
Do the integration by part too for the NLCC stress tensor contribution
Fix the sign of the individual components of the stress tensor, to avoid confusion
The NLCC term is printed independently of the XC term

Note that the last term is not the necessarily the same separation as in other codes.

News snippet

Small changes to the NLCC stress

Checklist

I have checked that my code follows the Octopus coding standards
I have added tests for all the new features added in this request.