Style guide part 7

This replaces the livepipe tabs with jQuery tabs. Please note that this PR is more for the functionality and not the style, which will take effect in a later PR.

This includes tabs on the manage groups/graders pages, spreadsheet graders page, marking panes, and student results panes.

Some of the "tabs" that actually just filter the tables are broken, but those will be changed with @oneohtrix 's new tables anyway.
@arkon With the `display:none` gone, if remark requests weren't visible (and so part of the jQuery tabs above), the div was appearing below the tabs, oddly. I'm not sure if you fixed this later, but I'm leaving the `style='display:none;'` in for now.