The old admin UI dashboard was still themed much like the Review Board

1.6 and 1.7 releases, and was very much showing its age. It wasn't

mobile-friendly, and had a sort of half-working support for

adding/removing/reordering widgets, which probably nobody used.
This change restyles the admin UI dashboard to fit in better with the

rest of the modern Review Board UI. It's cleaner, puts content first,

and works on both desktop and mobile.
It also temporarily removes the ability to reorder and to add/remove

widgets. These abilities are planned to come back, but with a different

implementation. For now, the "X" for deleting a widget still exists, but

won't work correctly.
Widgets themselves have a modern component-based set of CSS classes.

They're responsible for any of the styles they need within their content

area, rather than relying on some very situation-specific defaults that

were previously defined.
Upcoming changes will improve the layout of widgets, rewrite the

JavaScript backing to fix a lot of interaction quirks, add a better

structure for defining widgets, improve the representation of

information in existing widgets, and will either bring back the ability

to add/remove/reorder widgets or remove those capabilities entirely.

Tested that the widgets still work in mobile/desktop mode, and transition

between the modes correctly without rendering glitches.