libappfw|GuiWidget: Take opacity into account when blurring
Fixed: Compiler warning
libappfw: Inverted "info style" for MessageDialog and ButtonWidget

DialogContentStylist was also made somewhat more intelligent.
Tutorial|Client: New visual appearance

Background is blurred instead of darkened, and the tutorial popups
use the informational (inverted) style to stand out.

Added a special blurring widget behind the task bar that can be
shown to blur the entire view when needed.
libappfw: Added an inverted style for TabWidget
UI|Ring Zero: Use inverted style for game filter