Add Diesel and Refined Fuel to Forge Liquid Dictionary.
maybe also make refined Fuel equal to Buildcraft Fuel.

according to the code they are already registered in forge's FluidDictionary.
https://github.com/EternalBlueFlame/Traincraft-5/blob/1.7/src/main/java/train/common/api/LiquidManager.java#L56-L57

However The current system doesn't use classes to define the fluids, they are static variables, so we can't properly implement buildcraft's interfaces for fuel to the fluid objects.
There is an attempt at it here, but clearly not a working one anymore due to the required implementations in their API:
https://github.com/EternalBlueFlame/Traincraft-5/blob/1.7/src/main/java/train/common/api/LiquidManager.java#L77-L81