ATS - Cummins ISX Straight Pipe Sound V4.0

Version 4.0 Changelog:
-Renamed cm870 and cm2250 to ISX and ISX15 and will be stock EGR and VGT version
-EGR and VGT deleted version will be ISX with N14 turbo and ISX15 with Holset HX60W Turbo
-VGT Deleted ISX use jake brake, and the rest use interbrake
(Note: Because 3rd stage interbrake is done by VGT mechanism, so VGT Deleted ISX15 won't have difference between 2nd and 3rd stage)
-Removed X15 engine as it gonna be its own mod
-Whole new engine specifications
-Reworked sounds of course

Authors: SlavJerry