Simplify lamp logic, add new lights for 810 vehicles (#148)

Simplified lamp logic by reducing unnecessary brackets, `if` statements, ternary operators and boolean comparisons.
Added new lamps:
- `i-gear1` - 1st gear in the gearbox is active
- `i-gear2` - 2nd gear in the gearbox is active
- `i-hydrolockup` - The gearbox is locking the engine and wheels together

Additionally, fixed motor overload and differential relay lights not turning off when the battery is turned off.

vehicle/Train.h

@@ -759,6 +759,9 @@ public: // reszta może by?publiczna
     TButton btLampkaBocznik2;
     TButton btLampkaBocznik3;
     TButton btLampkaBocznik4;
+    TButton btLampkaGear1;
+    TButton btLampkaGear2;
+    TButton btLampkaHydroLockup;
     TButton btLampkaRadiotelefon; // TODO: implement
     TButton btLampkaHamienie;
     TButton btLampkaBrakingOff;