Merge branch 'master' of https://github.com/metabase/metabase into sync-ui-polish

docs/troubleshooting-guide/datawarehouse.md

frontend/src/metabase/css/components/table.css

frontend/src/metabase/css/core/colors.css

frontend/src/metabase/icon_paths.js

frontend/src/metabase/reducers-main.js

frontend/src/metabase/reference/components/Detail.jsx

...metabase/reference/components/EditableReferenceHeader.jsx

frontend/src/metabase/reference/reference.js

frontend/src/metabase/reference/selectors.js

frontend/src/metabase/routes.jsx

frontend/src/metabase/services.js

.../src/metabase/visualizations/components/Visualization.jsx

frontend/src/metabase/xray/Histogram.jsx

frontend/src/metabase/xray/components/CostSelect.jsx

frontend/src/metabase/xray/components/StatGroup.jsx

frontend/src/metabase/xray/components/XRayComparison.jsx

frontend/src/metabase/xray/containers/CardComparison.jsx

frontend/src/metabase/xray/containers/CardXRay.jsx

frontend/src/metabase/xray/containers/FieldComparison.jsx

frontend/src/metabase/xray/containers/FieldXray.jsx