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

tellico.desktop

@@ -3,7 +3,7 @@ Version=1.0
 Type=Application
 Exec=tellico -caption "%c" %i %u
 Icon=tellico
-DocPath=tellico/index.html
+X-DocPath=tellico/index.html
 Comment=A collection manager
 Comment[ru]=Менеджер коллекций
 Comment[cs]=Správce sbírek