ETS2 - Improvements and Rework NG Scania I6 Sound V1.5 (1.36.x)

A quick overview about what changed/reworked:
- realistic engine start sound interior/exterior
- realistic idle sound interior
- realistic engine off sound exterior
- added warning sound when turning off engine in the interior
- all sticks and switches recorded and added into the game
- real blinker sound

and much more...

Version 1.5:
- added realistic trailer-air-brake sound
- optimized some interior sound levels
- re-recorded blinker stick sound
- new handbrake-stick sounds

Authors: Max2712