feh.desktop: Add NoDisplay=true to hide feh from app menu (closse #228)

share/applications/feh.pre

 [Desktop Entry]
 Name=Feh
+Name[en_US]=feh
 GenericName=Image viewer
 GenericName[en_US]=Image viewer
 Comment=Fast Imlib2-based Image Viewer
@@ -9,4 +10,4 @@ Type=Application
 Icon=$IMAGEDIR$/feh.png
 Categories=Graphics;2DGraphics;Viewer;
 MimeType=image/bmp;image/gif;image/jpeg;image/jpg;image/pjpeg;image/png;image/tiff;image/x-bmp;image/x-pcx;image/x-png;image/x-portable-anymap;image/x-portable-bitmap;image/x-portable-graymap;image/x-portable-pixmap;image/x-tga;image/x-xbitmap;
-Name[en_US]=feh
+NoDisplay=true