Configure NSIS-packaged CMake version and install destination

Remove the version number from the default package install destination.
An unversioned default allows users to upgrade their CMake installations
without manually re-generating all their build trees to update the path
to CMake.  Users can select a versioned directory name on installation
if they wish.

Also name the package with the full CMake version number so it is clear
exactly what version is going to be installed.  This is particularly
helpful for the nightly binary installers.

CMakeCPack.cmake

@@ -29,27 +29,23 @@ if(EXISTS "${CMAKE_ROOT}/Modules/CPack.cmake")
   set(CPACK_PACKAGE_VENDOR "Kitware")
   set(CPACK_PACKAGE_DESCRIPTION_FILE "${CMAKE_CURRENT_SOURCE_DIR}/Copyright.txt")
   set(CPACK_RESOURCE_FILE_LICENSE "${CMAKE_CURRENT_SOURCE_DIR}/Copyright.txt")
+  set(CPACK_PACKAGE_NAME "${CMAKE_PROJECT_NAME}")
   set(CPACK_PACKAGE_VERSION "${CMake_VERSION}")
-  set(CPACK_PACKAGE_INSTALL_DIRECTORY "CMake ${CMake_VERSION_MAJOR}.${CMake_VERSION_MINOR}")
+  set(CPACK_PACKAGE_INSTALL_DIRECTORY "${CPACK_PACKAGE_NAME}")
   set(CPACK_SOURCE_PACKAGE_FILE_NAME "cmake-${CMake_VERSION}")
 
-  # Make this explicit here, rather than accepting the CPack default value,
-  # so we can refer to it:
-  set(CPACK_PACKAGE_NAME "${CMAKE_PROJECT_NAME}")
-
   # Installers for 32- vs. 64-bit CMake:
   #  - Root install directory (displayed to end user at installer-run time)
   #  - "NSIS package/display name" (text used in the installer GUI)
   #  - Registry key used to store info about the installation
   if(CMAKE_CL_64)
     set(CPACK_NSIS_INSTALL_ROOT "$PROGRAMFILES64")
-    set(CPACK_NSIS_PACKAGE_NAME "${CPACK_PACKAGE_INSTALL_DIRECTORY} (Win64)")
-    set(CPACK_PACKAGE_INSTALL_REGISTRY_KEY "${CPACK_PACKAGE_NAME} ${CPACK_PACKAGE_VERSION} (Win64)")
+    set(CPACK_NSIS_PACKAGE_NAME "${CPACK_PACKAGE_NAME} ${CPACK_PACKAGE_VERSION} (Win64)")
   else()
     set(CPACK_NSIS_INSTALL_ROOT "$PROGRAMFILES")
-    set(CPACK_NSIS_PACKAGE_NAME "${CPACK_PACKAGE_INSTALL_DIRECTORY}")
-    set(CPACK_PACKAGE_INSTALL_REGISTRY_KEY "${CPACK_PACKAGE_NAME} ${CPACK_PACKAGE_VERSION}")
+    set(CPACK_NSIS_PACKAGE_NAME "${CPACK_PACKAGE_NAME} ${CPACK_PACKAGE_VERSION}")
   endif()
+  set(CPACK_PACKAGE_INSTALL_REGISTRY_KEY "${CPACK_NSIS_PACKAGE_NAME}")
 
   if(NOT DEFINED CPACK_SYSTEM_NAME)
     # make sure package is not Cygwin-unknown, for Cygwin just