With everything now using GUI::FileIconProvider and therefore loading
icons embedded in the executable files, this information is now longer
being used.
We might have to think about this again if we want to allow .af files
with custom commands (e.g. shell scripts). Maybe those could get away
with just an "Icon" entry under "[App]", but currently there's only
"Executable" anyway.
This adds a new 32x32 Help application icon, a new open book icon,
copies the current book icon as Help's 16x16 icon, and updates
the Help application file to reflect these changes.
