
Sound fixes for Setra 415NF V2 and a new OM457 version.

I noticed some inconsitencies in Arne J's Setra 415NF v2 with regard to constfile and sound usages.
Now I fixed the naming/constfile/soundfile inconsistencies based on @Morpheus's Citaro Facelift v2.1, and added an 260kW OM457hLA version.

- adds a new variant of 260kW OM457hLA + ZF 6HP with High speed diff (5.21) to Setra 415NF V2
- fixed OM906 sounds and scripts based on Morpheus Citaro Facelift Pack 2.1

You may find the K++ patch by TheFMrr here: https://reboot.omsi-webdisk.de/file/5625-k-mod-for-the-setra-s415-nf-v2/