Improved weather fixing algorithms

...main/java/no/bioforsk/vips/entity/WeatherObservation.java

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

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

src/test/resources/swedishData.json

src/test/resources/swedishData_1.json

src/test/resources/swedishData_2.json