Warn that ctkDashboardDriverScript.cmake is on commontk.org

Dashboard scripts need to access this driver script before having downloaded CTK (because it's the script that does it). This is why the driver script is also available at http://commontk.org/ctkDashboardDriverScript.cmake.

CMake/ctkDashboardDriverScript.cmake

@@ -22,6 +22,10 @@
 # Included from a dashboard script, this cmake file will drive the configure and build
 # steps of the different CTK sub-project (library, application or plugins)
 #
+# ctkDashboardDriverScript.cmake is automatically downloaded by the dashboard script
+# from the url http://commontk.org/ctkDashboardDriverScript.cmake
+# \note Any change to the file should also be backported on http://commontk.org/
+#
 
 #-----------------------------------------------------------------------------
 # The following variable are expected to be define in the top-level script: