danwent
Only display 'private browsing' option for browsers that support it
Now that #115 is in and we respect private browsing settings, it is a bit confusing to open the Prefs dialog in SeaMonkey and see the checkbox, as SeaMonkey does not have private browsing mode.
It would be great if we could conditionally enable-disable this option in the prefs dialog, depending on whether the browser supported it. I don't think we should hide the option, as that may be confusing to the user. But if we could maybe disable the control and add text that says "feature unsupported in this browser" or something similar that would be great.
Maybe we want to tackle this now with some quick and easy browser check, or maybe leave it until the major "extract all browser specific code into its own javascript object" overhaul.
