When a datagrid is rendered on a small (<= 720px) screen, it now goes
into responsive mode. In this mode, the contents of the datagrid become
more vertical.

Each column that represents text or other complex data moves to its own
row. The column headers disappear, and instead move to the left-hand
side of the content on that row.

Each row is styled to appear as if it's all part of one big row. The
even/odd classes remain, and other classes are added to help properly
with border placement.

Columns that consist solely of icons continue to stay grouped together,
occupying the top row.

To get this layout, we have to do some work on the table. We run through
a copy of the datagrid's table, changing the layout of the contents, and
set that as the displayed table. The old one is preserved so we can
switch back to it if the window resizes large enough to go back into the
traditional mode.

Editing columns continues to work properly, as does reloading. However,
columns cannot be reordered in this mode.

In order to make clicking/tapping work better in this mode, we finally
have logic to allow clicking anywhere in the row to navigate to the
URL associated with that row. There's event handlers in place to ensure
that clicking a checkbox or some other item within the row will not
inadvertently go to the wrong URL, or prevent existing functionality
(like multi-row selection) from working.

Tested in responsive mode on Chrome, with a small window, and on the iPhone

in both portrait and landscape modes.
On all datagrids, the information was presented properly in a vertical mode.

I could tap anywhere to navigate to the review request, and I could also

toggle stars and checkboxes without navigating pages.
Editing columns in this mode worked properly.
Resizing kept all the page contents in the proper position. Going in and out

of responsive mode presented the correct views, without information loss

or any visual distortion.
Tested with a variety of columns. There's some cleanup we may want to do

for, say, the age-related columns, but that can be tackled separately.