Install desktop file and icons on Linux systems

[akien-mga]

Here's the desktop file I'm using for Mageia's wizznic package:

[Desktop Entry]
Name=Wizznic
Comment=Brick-matching puzzle game
GenericName=Puzzle game
Exec=wizznic
Icon=wizznic
Type=Application
Categories=Game;LogicGame;

This file should be installed as /usr/share/applications/wizznic.desktop.

The Icon=wizznic part will only work if an icon named wizznic.png (or wizznic.svg) is provided in at least one of these locations:

• /usr/share/icons/hicolor/*/apps
• /usr/share/icons
• /usr/share/pixmaps
  The "modern" way is to use the hicolor theme, so you could for example install data/wmicon.png to /usr/share/icons/hicolor/32x32/apps/wizznic.png

If high-res icons are provided (see #9), you can also install them in the corresponding folders in the hicolor theme (e.g. "128x128" or "scalable").

[akien-mga]

Note that I might do a pull request to implement that if you like the idea.