Issue #2321505 by LewisNyman: Split Seven's style.css into SMACSS categories.

core/modules/system/src/Tests/Menu/MenuRouterTest.php

core/modules/taxonomy/src/Tests/ThemeTest.php

core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php

core/themes/seven/css/base/elements.css

core/themes/seven/css/components/admin-list.css

core/themes/seven/css/components/admin-options.css

core/themes/seven/css/components/admin-panel.css

core/themes/seven/css/components/block-recent-content.css

core/themes/seven/css/components/branding.css

core/themes/seven/css/components/breadcrumb.css

core/themes/seven/css/components/comments.css

core/themes/seven/css/components/console.css

core/themes/seven/css/components/dialog.theme.css

core/themes/seven/css/components/entity-meta.css

core/themes/seven/css/components/field-ui.css

core/themes/seven/css/components/form.css

core/themes/seven/css/components/help.css

core/themes/seven/css/components/jquery.ui.theme.css

core/themes/seven/css/components/menus-and-lists.css

core/themes/seven/css/components/modules-page.css