Validate .desktop entry with desktop-file-utils 0.17.

--- gpa.desktop
+++ gpa.desktop
@@ -6,8 +6,7 @@
 GenericName[sv]=GNU Integritets-hjälpreda
 GenericName[en_US.ISO8859-1]=GNU Privacy Assistant
 Exec=gpa
-Icon=gpa.png
+Icon=gpa
 Terminal=false
-Encoding=UTF-8
 Type=Application
-Categories=GTK;Application;Security;Utility;
+Categories=GTK;Utility;System;Security;