Update README.md Datasets/Benchmark cases download

Description that the CMake file downloads certain benchmark cases/ test cases automatically and incorporates them in the framework in a seamless way.

README.md

@@ -164,6 +164,21 @@ For the purpose of code documentation, the <a href="https://www.doxygen.nl">Doxy
 
 to compile and generate the repository's documentation. The `DoxyfileConfig.in` can be adapted and supports HTML (see `GENERATE_HTML`), LaTex (see `GENERATE_LATEX`), RTF (see `GENERATE_RTF`), MAN page (see `GENERATE_MAN`), XML (see `GENERATE_XML`), and DOCBOOK (see `GENERATE_DOCBOOK`) output of the documentation. Initially only html and latex is generated. The output directory is under`./documentation` and can be changed at `OUTPUT_DIRECTORY` if necessary.
 
+<h2>Data</h2>
+
+As mentioned in "CMake Parameter Overrides" the CMake file downloads a lot of test cases itself denoted by `EGOA_DOWNLOAD_<dataset>`, which helps you to start your work faster. Each successful CMake run shows the downloaded dataset directories by
+
+```
+...
+-- Download of data sets:
+--  Download PyPSA Europe data from https://github.com/PyPSA/pypsa-eur.git into /Users/fwegner/Documents/Repositories/Public/EGOA/egoa/data/PowerGrids/PyPSA/pypsa-eur.
+--  Download PyPSA ITI Collaboration data from https://git.scc.kit.edu/FN/iti-collaboration.git into /Users/fwegner/Documents/Repositories/Public/EGOA/egoa/data/PowerGrids/PyPSA/pypsa-iti-collaboration.
+--  Download IEEE Power Grid data.
+...
+```
+
+At the moment this is limited to PyPSA and the IEEE cases and will be extended eventually to other test cases.
+
 <h2>Summary</h2>
 
 This repository is based on the PhD thesis <a href="http://dx.doi.org/10.5445/IR/1000120612">"Combinatorial Problems in Energy Networks -- Graph Theoretic Models and Algorithms"</a>. The Git repository of the PhD thesis is available under <a href="https://github.com/franziska-wegner/PhD_Thesis--Combinatorial_Problems_in_Energy_Networks--Graph_Theoretic_Models_and_Algorithms">Combinatorial_Problems_in_Energy_Networks</a>.