Added python helper files and cleanup of directories

...c/main/java/org/orekit/python/PythonAbstractDetector.java

.../src/main/java/org/orekit/python/PythonEventDetector.java

...s/src/main/java/org/orekit/python/PythonEventHandler.java

.../java/org/orekit/python/PythonOrekitFixedStepHandler.java

...main/java/org/orekit/python/PythonUnivariateFunction.java

...ditions/src/main/java/org/orekit/python/package-info.java

orekit-conda-recipe/meta.yaml

python_files/README.md

python_files/pyhelpers.py

python_files/test/AltitudeDetectorTest.py

python_files/test/BackAndForthDetectorTest.py

python_files/test/EventDetectorTest.py

python_files/test/EventHandlerTest.py

python_files/test/GroundFieldOfViewDetectorTest.py

python_files/test/ImpulseManeuverTest.py

python_files/test/IodGibbsTest.py

python_files/test/KeplerianConverterTest.py

python_files/test/NodeDetectorTest.py

python_files/test/SmallManeuverAnalyticalModelTest.py

python_files/test/TLEConverterTest.py