fix: Keyboard accessible context menus (#1768)

- Makes menus fully accessible and keyboard driven
- Currently adds 2.8% to initial bundle size due to the inclusion of Reakit and its dependency, popperjs.
- Converts all menus to functional components
- Remove old custom menu system
- Various layout and flow improvements around the menus

closes #1766

app/components/DocumentMeta.js

@@ -15,6 +15,7 @@ const Container = styled(Flex)`
   font-size: 13px;
   white-space: nowrap;
   overflow: hidden;
+  min-width: 0;
 `;
 
 const Modified = styled.span`