Clean / improve / update code

lib/match_page.dart

lib/models/game/board.dart

lib/models/game/game.dart

lib/models/settings/settings_game.dart

lib/models/settings/settings_global.dart

lib/player.dart

lib/robot/robot_player.dart

lib/ui/helpers/app_titles.dart

lib/ui/helpers/styled_button.dart

lib/ui/layouts/game_layout.dart

lib/ui/layouts/parameters_layout.dart

lib/ui/parameters/parameter_painter.dart

lib/ui/parameters/parameter_widget.dart

lib/ui/screens/page_about.dart

lib/ui/screens/page_game.dart

lib/ui/screens/page_settings.dart

lib/ui/settings/settings_form.dart

lib/ui/settings/theme_card.dart

lib/ui/skeleton.dart

lib/ui/widgets/actions/button_delete_saved_game.dart