add README to KHI test and include it in documentation

docs/source/index.rst

@@ -72,6 +72,7 @@ In case you are already fluent in compiling C++ projects and HPC, running PIC si
    usage/picmi/index
    usage/python_utils
    usage/examples
+   usage/tests
    usage/workflows
    usage/crosscompile
 

docs/source/tests

@@ -0,0 +1 @@
+../../share/picongpu/tests

docs/source/usage/tests.rst

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+.. _usage-tests:
+
+Test Setups
+===========
+
+.. toctree::
+   :glob:
+   :maxdepth: 1
+
+   ../tests/*/README

share/picongpu/tests/KHI_growthRate/README.rst

@@ -0,0 +1,39 @@
+KelvinHelmholtz: Kelvin-Helmholtz Instability
+=============================================
+
+.. sectionauthor:: Richard Pausch <r.pausch (at) hzdr.de>
+.. moduleauthor:: Richard Pausch <r.pausch (at) hzdr.de>, Mika Soren Voß <m.voss (at) hzdr.de>
+
+This KHI growth rate test simulates a shear-flow instability known as the Kelvin-Helmholtz Instability in a sub-relativistic setup as studied in [Alves12]_, [Grismayer13]_, [Bussmann13]_. The setup uses a pre-ionized quasi-neutral hydrogen plasma. From the simulation, the growth of the dominant magnetic field is extracted and compared to theoretic predictions. The tests only passes if the simulation reaches the ideal theoretical growth rate with a 10% accuracy. 
+
+
+Usage
+-----
+
+.. code-block:: bash
+
+  # execute ci
+  $PICSRC/share/picongpu/tests/KHI_growthRate/bin/ci.sh $PICSRC/share/picongpu/tests/KHI_growthRate/ <user_given_output_directory>
+
+
+References
+----------
+
+.. [Alves12]
+       E.P. Alves, T. Grismayer, S.F. Martins, F. Fiuza, R.A. Fonseca, L.O. Silva.
+       *Large-scale magnetic field generation via the kinetic kelvin-helmholtz instability in unmagnetized scenarios*,
+       The Astrophysical Journal Letters (2012),
+       https://dx.doi.org/10.1088/2041-8205/746/2/L14
+
+.. [Grismayer13]
+       T. Grismayer, E.P. Alves, R.A. Fonseca, L.O. Silva.
+       *dc-magnetic-field generation in unmagnetized shear flows*,
+       Physical Reveview Letters (2013),
+       https://doi.org/10.1103/PhysRevLett.111.015005
+
+.. [Bussmann13]
+       M. Bussmann, H. Burau, T.E. Cowan, A. Debus, A. Huebl, G. Juckeland, T. Kluge, W.E. Nagel, R. Pausch, F. Schmitt, U. Schramm, J. Schuchart, R. Widera.
+       *Radiative Signatures of the Relativistic Kelvin-Helmholtz Instability*,
+       Proceedings of the International Conference on High Performance Computing, Networking, Storage and Analysis (2013),
+       http://doi.acm.org/10.1145/2503210.2504564
+