Fudge the height of the page for long listing choosers.

This is a hack to ensure that the listing chooser is entirely visible on
the page until we can improve the positioning/scrolling of the listing
chooser sidebar.
Use background attachment to position sidebar grippy image.

Fixed positioning was causing the grippy image to bleed out of the
sidebar when scrolling horizontally on small viewports.
Add hover tooltip for ellipsized multi names.
Fix the column widths of the user page multi list.

The width of em units were varying across platforms wrt the box size.