Negative pumping_speed with optional pollution

[mknejp]

Is it possible to make the "offshore-pump" prototype work with negative "pumping_speed" values to dump their content out into the water? This would be useful for a waste disposal mod introducing additional complexity.

Along with it would be interesting to add a "pollution" value (default=0) to fluids indicating how much pollution is generated per unit of fluid that is dumped into the environment where the pump is located. This would incentivise players to apply treatment before releasing waste fluids to the environment.