Wrong error message when trying to rate more then once

[Kirby]

If I try to rate an image more than once I get an error telling me that I have already rated this thread.

This is confusing, as I am rating an image - not a thread.

Also the redirect-messages after rating an image refer to threads.

[Zachariah]

Added 2 new phrases.
- adv_gallery_imageratevoted
- adv_gallery_imagerate_update

changed threadratevoted to adv_gallery_imageratevoted
changed redirect_threadrate_update to adv_gallery_imagerate_update

Updated /gallery/newreply.php