Fluid wagon filters

[ItzPratix]

TL;DR

Prevent pumps from pumping any unfiltered fluid into a fluid wagon by setting a filter on the fluid wagon.

Why?

In the case you have a station being used by multiple trains with fluid wagons with different purposes it can become annoying when the wrong fluid is being pumped into the wrong fluid wagon. Having a simple filter on fluid wagons similar to how you can filter cargo wagons would allow more flexibility with trains.