Use a better default installation directory for Debian systems

Contributes to Ultimaker/Uranium#42

CMakeLists.txt

@@ -58,9 +58,13 @@ endif()
 include(GNUInstallDirs)
 find_package(PythonInterp 3.4.0 REQUIRED)
 
-set(PYTHON_SITE_PACKAGES_DIR ${CMAKE_INSTALL_PREFIX}/lib/python${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}/site-packages CACHE PATH "Install location of Python package")
 install(DIRECTORY resources DESTINATION ${CMAKE_INSTALL_DATADIR}/cura)
-install(DIRECTORY plugins DESTINATION ${CMAKE_INSTALL_PREFIX}/lib/cura)
-install(DIRECTORY cura DESTINATION ${PYTHON_SITE_PACKAGES_DIR})
-install(FILES cura_app.py DESTINATION ${CMAKE_INSTALL_BINDIR})
+install(DIRECTORY plugins DESTINATION lib/cura)
+install(FILES cura_app.py DESTINATION ${CMAKE_INSTALL_BINDIR} PERMISSIONS OWNER_READ OWNER_WRITE OWNER_EXECUTE GROUP_READ GROUP_EXECUTE WORLD_READ WORLD_EXECUTE)
+if(NOT APPLE AND NOT WIN32)
+    install(DIRECTORY cura DESTINATION lib/python${PYTHON_VERSION_MAJOR}/dist-packages)
+    install(FILES cura.desktop DESTINATION ${CMAKE_INSTALL_DATADIR}/applications)
+else()
+    install(DIRECTORY cura DESTINATION lib/python${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}/site-packages)
+endif()