Alpha Trolleybus Skoda 14Tr 2.1

- US-like and UA-like livery
- service unit (with working beacons)
- added second diesel trailer (yellow with beacon)
- added trolleybus train unit (Skoda TV - 14Tr). Basically just a 14Tr with tow bar which can compose trolleybus train by using them as trailer. LUA scripting for steering as "сцепка" (working just on the first trailer unit, the other ones copy the same).