Better generator input fluid temperatures

[SWeini]

Right now the input fluid temperature is the temperature in the fluidbox. If it's empty it is the max supported temperature, which is not always the best choice.

Possible improvements:

1. Follow (ghost) pipes to find the production temperature of the steam. Ghosts make this non-trivial. Also need some max distance to follow.
2. Round input fluid temperature to generated temperature if it's close enough.
3. Return a meta configuration with children for all normal input temperatures. If there is a temperature from the fluidbox the ratio can be calculated in a way that simulates fluid temperature mixing. If used in a larger context, it's possible to filter out children with temperatures that aren't produced anywhere.