Fix ServiceTypes, ExcludeServiceTypes, and DocPath desktop file entries to match XDG specifications

kdirstat/kdirstat.desktop

@@ -3,7 +3,7 @@ Type=Application
 Exec=kdirstat -caption "%c" %i %m
 Icon=kdirstat
 MiniIcon=kdirstat
-DocPath=kdirstat/index.html
+X-DocPath=kdirstat/index.html
 Encoding=UTF-8
 Comment=Directory statistics and disk usage
 Comment[de]=Verzeichnisstatistik und Platzverbrauch