CMake: uniformly no redundant, unchecked argument to endif etc

App/CMakeLists.txt

CMakeLists.txt

GUI/CMakeLists.txt

cmake/BornAgain/Config.cmake

cmake/BornAgain/Directories.cmake

cmake/BornAgain/MakeLib.cmake

cmake/BornAgain/PackDebian.cmake

cmake/BornAgain/PythonDocs.cmake

cmake/BornAgain/SwigLib.cmake

cmake/configurables/FixPack.cmake.in

cmake/multipython/FindCustomPython3.cmake

cmake/multipython/MakePythonWheel.cmake

cmake/multipython/PyDependences.cmake