Individual Responses table improvements

Nobody has claimed this yet.

These were some improvements to the Individual Responses table that didn't make it into the last release. We want the table to be a little clearer and more dynamic.

- The table should let you click on a column to hide or filter (which means we can remove the show/hide column links at the top). If columns are hidden or filtered, there should be an indicator at the top that you can clear (e.g. "N columns hidden", "show all columns" button)
- The table should be paginated, and the pagination should update when filters (row numbers) change.
- Figure out how to fix the issue with the selected row being unclear (currently a row remains selected even when not shown on the page, e.g. because a filter was applied, which is confusing).

# Implementation

- We could keep datatables and implement this in JavaScript.
- We could switch to a different library: [Tabulator](https://tabulator.info/), [AG Grid (Community Edition)](https://www.ag-grid.com/community/), [Grid.js](https://gridjs.io/), [Handsontable](https://handsontable.com/), others?

Start by locating the Individual Responses table and reviewing its current DataTables integration. Compare the proposed JavaScript approaches, then define the column hiding/filtering indicator, pagination updates, and selected-row behavior as the completion criteria.

Written by the indexing model from the issue text.