[MTR4] CP 3400 Series

Fixed the following bugs:

• The door's interior would render with the exterior lighting, resulting on a darkned colour during the nighttime
• Trains without a pantograph could be unstable and play the pantograph's sounds constantly
• Various other minor fixes and Added the following features:
• Added scripted interior displays
  • You can customize these by extracting the pack and modifying the assets/mtr/cp_3400/config.js file, following the instructions provided
• Added custom overlays/displays
  • These overlays can be added to assets/cp3400/custom_overlays and should use the template in that folder (TEMPLATE.png).
  • To spawn a train with an overlay, change the train's siding name to OVERLAY=FILENAME1,FILENAME2
  • For example: OVERLAY=myOperator renders the myOperator overlay on all carriages, whilst OVERLAY=ad1,ad2 renders ad1 on the 1st, 3rd... carriages and ad2 on the 2nd, 4th, 6th... carriages
• Added an experimental door side indicator
  • To use this feature, add a station exit to any station and set the exit's name to DR ("doors on the right"), DL ("doors on the left") or DB ("doors on both sides) and the number to the platform number.
  • I.e. DR & 2 specifies that, on platform 2, at that station, the doors will open on the right.