Add python version (2 or 3) to Windows installers

cmake/bornagain/modules/CPackWindows.cmake

-# BornAgain Windows packaging 
+# BornAgain Windows packaging
 
-set(CPACK_GENERATOR "NSIS")  
+if(BORNAGAIN_USE_PYTHON3)
+  set(WIN_PYTHON_VERSION "python3")
+else()
+  set(WIN_PYTHON_VERSION "python2")
+endif()
+
+set(CPACK_PACKAGE_FILE_NAME
+    "${CMAKE_PROJECT_NAME}-${BORNAGAIN_VERSION}-${BORNAGAIN_ARCHITECTURE}-${WIN_PYTHON_VERSION}")
+
+set(CPACK_GENERATOR "NSIS")
 
 #set(CPACK_NSIS_MODIFY_PATH ON)
 set( CPACK_NSIS_INSTALL_ROOT "C:")
@@ -14,23 +23,23 @@ set( CPACK_NSIS_MUI_ICON "${CMAKE_CURRENT_SOURCE_DIR}/GUI\\\\coregui\\\\images\\
 set( CPACK_NSIS_MUI_UNIICON "${CMAKE_CURRENT_SOURCE_DIR}/GUI\\\\coregui\\\\images\\\\BornAgain.ico" )
 
 set (CPACK_NSIS_EXTRA_INSTALL_COMMANDS "
-  Push \\\"PATH\\\" 
-  Push \\\"P\\\" 
-  Push \\\"HKCU\\\" 
-  Push \\\"$INSTDIR\\\\bin\\\" 
+  Push \\\"PATH\\\"
+  Push \\\"P\\\"
+  Push \\\"HKCU\\\"
+  Push \\\"$INSTDIR\\\\bin\\\"
   Call EnvVarUpdate
   Pop  \\\$0
 
-  Push \\\"PYTHONPATH\\\" 
-  Push \\\"P\\\" 
-  Push \\\"HKLM\\\" 
-  Push \\\"$INSTDIR\\\\bin\\\" 
+  Push \\\"PYTHONPATH\\\"
+  Push \\\"P\\\"
+  Push \\\"HKLM\\\"
+  Push \\\"$INSTDIR\\\\bin\\\"
   Call EnvVarUpdate
   Pop  \\\$0
 
   CreateShortCut \\\"$DESKTOP\\\\BornAgain.lnk\\\" \\\"$INSTDIR\\\\bin\\\\BornAgain.exe\\\"
 ")
-        
+
 set (CPACK_NSIS_EXTRA_UNINSTALL_COMMANDS "
   Push \\\"PATH\\\"
   Push \\\"R\\\"