Adjust realistic braking physics

Realistic acceleration uses 4 x the mass for acceleration as braking
Use 4 x mass for realistic braking as well to match
Increase per train length braking force
Add a power-based per train length braking force

src/train.h

@@ -71,6 +71,11 @@ enum ConsistChangeFlags {
 };
 DECLARE_ENUM_AS_BIT_SET(ConsistChangeFlags)
 
+enum RealisticBrakingConstants {
+	RBC_BRAKE_FORCE_PER_LENGTH      = 1600,      ///< Additional force-based brake force per unit of train length
+	RBC_BRAKE_POWER_PER_LENGTH      = 15000,     ///< Additional power-based brake force per unit of train length (excludes maglevs)
+};
+
 byte FreightWagonMult(CargoID cargo);
 
 void CheckTrainsLengths();