For the set of selected users when using a related users selector

widget, things were wrapping in terrible ways if there were long

usernames or real names. This change builds on a change in Djblets to

use a <table> for the layout of the options instead of a <ul>.
While in here, I also decided to make the widget a bit bigger, because

it was pretty small even for reasonable-sized desktop windows.

Created some users with very long names and added them to a group. Saw

that the users selector widget no longer looked terrible.