The widget adder dialogs were using jQuery UI's $.dialog, which at

some point got screwed up. This resulted in ugly dialogs with broken

CSS, a modal background which wasn't correct (was shown over the widget

itself and didn't scroll with the page), and it didn't fit visually with

the rest of the UI.
This change ports it over to use our $.modalBox, which is what

everything else uses for modals. This makes it fit in with our UI, and

just generally function correctly.

Added and removed both small and large widgets and saw that the dialog

displayed correctly.