BUG: Add the extension third party directories to additional launcher settings

This change will cause a change to the inner build
AdditionalLauncherSettings.ini file in extensions with a superbuild
set up, adding the top level extension third party lib and bin
directories to the library paths and paths settings. This fixes
tests in the SlicerOpenCV extension.

The support for Slicer_THIRDPARTY_BIN_DIR and Slicer_THIRDPARTY_LIB_DIR was
initially added in r25182 (BUG: Extension packaging: Support fixup of
3rd-party (external proj) libs)

See issue SBU-BMI/SlicerOpenCV#37

From: Nicole Aucoin <nicole@bwh.harvard.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25288 3bd1e089-480b-0410-8dfb-8563597acbee