Added remarks and corrected getSeasonSpan in Util.class (Aurelian did so)
Added compareDoubles method to Util.class and some changes in CO2Value.class

- overrode equals method for CO2Value
- changed constructor so that one does not need to fill in the
totalValue
Started Util test

Still to test:
- getCO2ValuesRecipes()
- getSeasonQuotient()
- getSeasonSpan()