Clean / improve / update code

lib/ui/widgets/actions/button_game_quit.dart

lib/ui/widgets/actions/button_game_start_new.dart

lib/ui/widgets/actions/button_resume_saved_game.dart

lib/ui/widgets/global_app_bar.dart

pubspec.lock

pubspec.yaml

resources/app/build_application_resources.sh

resources/build_resources.sh

resources/ui/build_ui_resources.sh

resources/ui/images/button_back.svg

resources/ui/images/button_delete_saved_game.svg

resources/ui/images/button_resume_game.svg

resources/ui/images/button_start.svg