ENH: Explicitly recognize virtual functions in applications

        clang-tidy tool can insert missing override keyword as a macro so that missing [optional] virtual identifiers can be easily added.

        build otb with clang 3.8 and use cmake option CMAKE_EXPORT_COMPILE_COMMANDS=ON. Most modules and third parties have been activated.

        #Run clang modernize check using utility script which allow to process the code in parallel (only on Applications directory)
        python run-clang-tidy.py -clang-tidy-binary ~/software/clang+llvm-3.8.0-x86_64-linux-gnu-ubuntu-14.04/bin/clang-tidy -checks=-*,modernize-use-override -header-filter=/home/grizonnetm/projets/otb/src/OTB/Modules/Modules/Applications/.*/include/.* -j8 -fix -p ~/projets/otb/bin/release/OTB-clang3.8/ ~/projets/otb/src/OTB/Modules/Applications/*/app/*.cxx  > ~/temporary/run-clang-tidy-app-log.txt

        #Replace override by ITK macro (to maintain compat with c++98) in Modules/Applications
        find . -type f -print -name "*.cxx" |xargs perl -pi -e 's/\ override/\ ITK_OVERRIDE/g'