Create dataset info drawer (#1805)

* create infoDrawer

* create read/writes to redux store

* reimplement reducer that vanished

* remove aboutURL stuff from title

* add formatting and style

* s/length/size and make metadata items list items

* remove comment

* remove empty singletons

* refactor into async react component

* Clean up skeleton

* swap out for loop for map

* add comment

* replace placeholder

* switch ternary for `&&`

* event handling fixes and PR feedback

* add button and move click handler to button

* ditch empty categories

* move drawer button handling to redux

* remove categorical move note

* PR feedback from colin

* update snapshot

* remove hover state

client/src/components/categorical/category/index.js

@@ -491,19 +491,7 @@ const CategoryRender = React.memo(
       /*
       Entire category has a single value, special case.
       */
-      const theOneValue = categorySummary.categoryValues[0];
-      return (
-        <div style={{ marginBottom: 10, marginTop: 4 }}>
-          <Truncate>
-            <span style={{ maxWidth: 150, fontWeight: 700 }}>
-              {metadataField}
-            </span>
-          </Truncate>
-          <Truncate>
-            <span style={{ maxWidth: 150 }}>{`: ${theOneValue}`}</span>
-          </Truncate>
-        </div>
-      );
+      return null;
     }
 
     /*