Lots of cool (or rather HOT) weather stuff

src/main/java/no/nibio/vips/model/maths/NonLinearCurves.java

src/main/java/no/nibio/vips/util/WeatherUtil.java

...t/java/no/nibio/vips/model/maths/NonLinearCurvesTest.java

src/test/java/no/nibio/vips/util/SolarRadiationUtilTest.java

src/test/java/no/nibio/vips/util/WeatherUtilTest.java