Add column description to table viz (#4831)

* Add column description to table viz

* Fix: misplaced super long titles tooltip.

client/app/visualizations/table/Editor/ColumnEditor.jsx

@@ -46,6 +46,14 @@ export default function ColumnEditor({ column, onChange }) {
         </Checkbox>
       </Section>
 
+      <Section>
+        <Input
+          label="Description"
+          defaultValue={column.description}
+          onChange={event => handleChangeDebounced({ description: event.target.value })}
+        />
+      </Section>
+
       <Section>
         <Select
           label="Display as:"

client/app/visualizations/table/utils.js

@@ -64,6 +64,13 @@ export function prepareColumns(columns, searchInput, orderBy, onOrderByChange) {
       align: column.alignContent,
       title: (
         <React.Fragment>
+          {column.description && (
+            <Tooltip placement="top" title={column.description} className="p-r-5">
+              <div className="table-visualization-heading">
+                <i className="fa fa-info-circle" aria-hidden="true"></i>
+              </div>
+            </Tooltip>
+          )}
           <Tooltip placement="top" title={column.title}>
             <div className="table-visualization-heading" data-sort-column-index={sortColumnIndex}>
               {column.title}