Add BPM horizontal cover with old appid for non-Steam games

[SantaHey]

As said in the Issue 61, BPM covers don't update with actual release. @aranel616 fixed the issue with the commit 6222596 but fixes it only on the import, not on updating covers.

I saw that @kongomongo fixes it in pull 117 on covers update too. But his code adds an asset for every type of covers and for every game, even Steam games which result with undefined files.

My commit fixes it only for horizontalGrid and only for Non-Steam games (Steam games use usual ID for BPM pictures)