Source term for axisymmetry in species transport

[lkusch]

Proposed Changes

This adds the source term for axisymmetry to the residual computation for species transport. The source term is zero for non-axisymmetric cases.

Related Work

This builds upon the closed pull request #1762 and is connected to #card-71271518 as an aspect of feature_flamelet.
The change uses the implementation by @bigfooted on feature_flamelet. The implemented source term was checked against literature/own derivation by @Cristopher-Morales.
I would like to set up a regression test as soon as #1784 is merged.

PR Checklist

• [x ] I am submitting my contribution to the develop branch.
• [x ] My contribution generates no new compiler warnings (try with --warnlevel=3 when using meson).
• [x ] My contribution is commented and consistent with SU2 style (https://su2code.github.io/docs_v7/Style-Guide/).
• I have added a test case that demonstrates my contribution, if necessary.
• I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp), if necessary.

[bigfooted]

@lkusch if it's good to go, please remove WIP from the title.

[pcarruscag]

This LGTM but it would be good to use in a regression at some point.
It would be good to have start having some more formal V&V for species transport @bigfooted @Cristopher-Morales

[bigfooted]

This LGTM but it would be good to use in a regression at some point. It would be good to have start having some more formal V&V for species transport @bigfooted @Cristopher-Morales

Good, we'll add these V&V, the results from my first attempt after a 2 week su2 crash course with Tom: https://su2code.github.io/documents/dev_meeting_2018/03_su2_dev_beishuizen.pdf