Bug 588462 - Use a plain black panel with a different layout

Bug 588462 - Use a plain black panel with a different layout

The semi-transparent gradient on the panel is replaced by a
solid black background. The shadow below the panel is removed.
The clock is put at the center instead of the right side of
the panel and has the date removed. The user icon is hidden.
Instead of boldface, a regular font is used. Padding is added
on each side and between panel elements.

button.js: Allow for custom text colors and fonts.
panel.js: Change the panel colors and layout, remove the shadow.