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
Tutorial: Improved content

Be more informative and use better terminology.
Fixed|Task Bar: When open, eat modifier key events

When the task bar is open, we shouldn't wake up the game by giving it
stray modifier events (e.g., when typing in the console).
Default Style: Made window background image a bit lighter
Fixed|Tutorial: Spurious format arg
Tutorial: Delay tutorial autostart a little
Tutorial|Console: Added a console command to start the tutorial
SDK|Documentation|Cleanup: Added sdk.doxy, cleaned up some Doxygen errors

There is now a combined API doc for the entire SDK, although some errors
remains (e.g., with class hierarchies being confused between libappfw
and libshell).
SDK|Fixed: Doxygen issues
libdeng2|SavedSessionMetadata: Use a ruleset block element for gamerules, tweaked alignment
Merge remote-tracking branch 'remotes/origin/master' into savegame-refactor