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

diff --git a/src/videopreview.desktop b/src/videopreview.desktop
index d755d18..b7f5559 100644
--- a/src/videopreview.desktop
+++ b/src/videopreview.desktop
@@ -54,7 +54,7 @@
 Name[zh_HK]=������������ (MPlayerThumbs)
 Name[zh_TW]=������������ (MPlayerThumbs)
 Name[zu]=Amafayela Evidiyo (MPlayerThumbs)
-ServiceTypes=ThumbCreator
+X-TDE-ServiceTypes=ThumbCreator
 CacheThumbnail=true
 IgnoreMaximumSize=true
 MimeTypes=video/*,application/vnd.ms-asf,application/vnd.rn-realmedia