Rename horizon settings filenames

The purpose of this patch is to make it easier to
review changes, because renaming and changing the
file in one patch will generate diff when the entire
file will be deleted on the one hand and new file
(actually just renamed) will be new on the other hand,
which is hard to review.

Change-Id: I17a16ce746faa8898a457cadbb6f996f964a5b6f