Add Support for browser.tabs.fadeLabels in PM 32.1

[stux2000]

The beta for PM 32.1 changes how long tab names are handled. Instead of cutting off the name with an ellipsis (...), the name simply fades. This behavior is now handled by the following about:config option:

• browser.tabs.fadeLabels

This enhancement would add a checkbox to the "Tab Bar" section under "Apperance" in the "Tab Utilities Options" screen. It should say something like "Fade Tab Labels" or similar.

[stux2000]

Important note: The UI should only display the new checkbox if the about:config option itself exists. Otherwise, it should remain unavailable for compatibility with older versions of the browser.