[py] Added requirements.txt and example usage for BHE benchmark.

.gitignore

@@ -17,6 +17,7 @@ conaninfo.txt
 CMakeLists.txt.user*
 
 *.pyc
+.venv
 
 Tests/**/*.md5
 Tests/Data/Parabolic/HT/InvalidProjectFiles/*.prj

Tests/Data/Parabolic/T/3D_3BHEs_array/README.md

+# How to run
+
+ You need to build OGS with `OGS_USE_PYTHON=ON` and have the Python modules
+ listed in `requirements.txt` installed, e.g.:
+
+ - In this directory:
+   - `virtualenv .venv` Make sure you use the same Python interpreter which was
+     embedded into OGS (look for `Found PythonInterp: ..` in the CMake output)
+   - `source .venv/bin/activate`
+   - `pip install -r requirements.txt`
+   - `PYTHONPATH=.venv/lib/python3.7/site-packages ~/code/ogs6/build/bin/ogs -o ~/tmp 3bhes_1U.prj`

Tests/Data/Parabolic/T/3D_3BHEs_array/requirements.txt

+TESPy==0.1.3