update application icons for iOS 7 (downscale from appstore icon)

the previous version of the icons used a transparent border, in an
attempt to preserve the icon designer's rendering at the original size.
unfortunately, a transparent border is rendered on actual devices as a
black border, which looks very ugly.

while scaling an image down from a larger size is also not ideal (the
final icon might contain scaling artifacts), in this situation it is
clearly the lesser of two evils.
"Game Actions" menu is now displayed in a popover on iPad (fixes #232)