Merge pull request #4883 from metabase/add-query-average-execution-times-to-dashcards

frontend/src/metabase/dashboard/components/DashCard.jsx

frontend/src/metabase/dashboard/components/DashCard.spec.js

frontend/src/metabase/dashboard/components/DashboardGrid.jsx

frontend/src/metabase/dashboard/containers/DashboardApp.jsx

frontend/src/metabase/dashboard/dashboard.js

frontend/src/metabase/dashboard/selectors.js

frontend/src/metabase/public/containers/PublicDashboard.jsx

src/metabase/api/dashboard.clj

src/metabase/api/dataset.clj

src/metabase/api/public.clj

test/metabase/api/dashboard_test.clj

test/metabase/test/util.clj