ENH: Update extension driver dashboard script to display variables.

This will facilitate understanding of the build context.

Here is an example of output:

$ ctest -S slicer_extensions_testing_experimental.cmake -VV

• Extra verbosity turned on
  Reading Script: /home/jcfr/Projects/sandbox/slicer_extensions_testing_experimental.cmake
  -- Setting 'MIDAS_PACKAGE_URL' variable with default value 'http://slicer.kitware.com/midas3'
  -- Setting 'MIDAS_PACKAGE_EMAIL' variable with environment variable value 'OBFUSCATED'
  -- Setting 'MIDAS_PACKAGE_API_KEY' variable with environment variable value 'OBFUSCATED'
  -- Setting 'run_ctest_submit' variable with default value 'TRUE'
  -- Setting 'run_ctest_with_update' variable with default value 'TRUE'
  -- Setting 'run_ctest_with_configure' variable with default value 'TRUE'
  -- Setting 'run_ctest_with_build' variable with default value 'TRUE'
  -- Setting 'run_ctest_with_notes' variable with default value 'TRUE'
  -- Setting 'Slicer_UPLOAD_EXTENSIONS' variable with default value 'TRUE'
  -- CTEST_SITE ........................: cerrotorre.kitware
  -- CTEST_BUILD_NAME ..................: Linux-g++5.2.1-64bits-QT4.8.7-PythonQt-With-Tcl-CLI-origin-master-Release
  -- SCRIPT_MODE .......................: experimental
  -- CTEST_BUILD_CONFIGURATION .........: Release
  -- ADDITIONAL_CMAKECACHE_OPTION ......:

-- CTEST_NOTES_FILES .................: /home/jcfr/Projects/sandbox/slicer_extensions_testing_experimental.cmake
-- CTEST_DASHBOARD_ROOT ..............: /home/jcfr/Projects/
-- CTEST_CMAKE_GENERATOR .............: Unix Makefiles
-- CTEST_TEST_TIMEOUT ................: 500
-- CTEST_BUILD_FLAGS .................: -j8
-- CTEST_PROJECT_NAME ................: Slicer4
-- EXTENSIONS_TRACK_QUALIFIER ........: master
-- EXTENSIONS_BUILDSYSTEM_SOURCE_DIRECTORY: /home/jcfr/Projects//Slicer/Extensions/CMake
-- EXTENSIONS_BUILDSYSTEM_TESTING ....: TRUE
-- EXTENSIONS_INDEX_GIT_REPOSITORY ...: git://github.com/Slicer/ExtensionsIndex.git
-- EXTENSIONS_INDEX_GIT_TAG ..........: origin/master
-- CTEST_BINARY_DIRECTORY ............: /home/jcfr/Projects//SlicerExtensions-build-64bits-QT4.8.7-PythonQt-With-Tcl-CLI-Release-experimental-Testing-master
-- CTEST_SVN_COMMAND .................: /usr/bin/svn
-- CTEST_GIT_COMMAND .................: /usr/bin/git
-- Slicer_DIR ........................: /home/jcfr/Projects//Slicer-Release/Slicer-build
-- CTEST_CONFIGURATION_TYPE ..........: Release
-- CTEST_LOG_FILE ....................: NOT DEFINED
-- CTEST_NOTES_FILES .................: /home/jcfr/Projects/sandbox/slicer_extensions_testing_experimental.cmake
-- CTEST_PARALLEL_LEVEL ..............: 8
-- MIDAS_PACKAGE_URL .................: http://slicer.kitware.com/midas3
-- run_ctest_submit ..................: TRUE
-- run_ctest_with_update .............: TRUE
-- run_ctest_with_configure ..........: TRUE
-- run_ctest_with_build ..............: TRUE
-- run_ctest_with_notes ..............: TRUE
-- Slicer_UPLOAD_EXTENSIONS ..........: TRUE
-- CTEST_SOURCE_DIRECTORY ............: /home/jcfr/Projects//Slicer/Extensions/CMake
-- Slicer_EXTENSION_DESCRIPTION_DIR ..: NOT DEFINED
-- empty_binary_directory ............: FALSE
-- force_build .......................: TRUE
-- model .............................: Experimental
-- track .............................: Extensions-Experimental
-- CTEST_USE_LAUNCHERS ...............: 1
[...]

From: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24987 3bd1e089-480b-0410-8dfb-8563597acbee