Capitalize the tab titles of the prefs dialog.

Ok, one more. This one might seem trivial, but I really think that the tab labels, being titles, should be capitalized. I got used to the all-lowercase labels in most dialogs. (I do think that group labels should also be capitalized there to improve readability, but I can live with the way it is now.) But lowercase tab titles just look wrong to me, I can't help it. :) Button labels and menu entries are also capitalized for a reason, and I think that tab titles belong to the same category.