message: Updated Contributors; UI-QT: updated "About".
  clean.sh now does not seach all subdirectories.
diff: find ./build ! -name .gitkeep ! -wholename ./build -delete
  rm -rf Debug
  rm -rf Release
  -find . -wholename ./spirit* -delete
  +find . -maxdepth 1 -wholename ./spirit* -delete
  find ./core/python/Spirit -mindepth 1 -name *Spirit* -delete
  find ./core/julia/Spirit -mindepth 1 -name *Spirit* -delete
  find ./ui-web -mindepth 1 -name spirit.js* -delete
  