rename README -> README.md; uniform subdirectory name Python/, not

ThirdParty/Core/tspectrum/README.md

Wrap/Python/README.md

Wrap/Python/__init__.py.in

Wrap/Python/bornagain_python_install.py

Wrap/Python/plot_utils.py

auto/README.md

auto/Wrap/doxygenSample.i

cmake/BornAgain/Config.cmake

cmake/BornAgain/Directories.cmake

cmake/BornAgain/NixInstall.cmake

cmake/BornAgain/PythonAPI.cmake

devtools/README.md

devtools/profiling/README.md