Improvements to Climates and Seasons

[apoapostolov]

Related but not duplicate of #71

Please allow us to configure custom Climates with its own chance of specific conditions and temperature range. The predefined ones aren't working well for me, I have generated horribly low values for summer weather in temperate regions (15C to -7C daytime) which is very unrealistic and I have to wing it with players not to lose them to disbelief.

[LeRatierBretonnien]

yes ! ok