Manage the number of days by a year according to the complete leap cycle of 400 years

It's not important, but it doesn't cost anything to change (except the temporary setting in the .regressionignore file).

Currently airGR use 365.25 day by a year. According to the complete leap cycle of 400 years, he true value should be 365.2425.

Have to be take into account in the following functions:

• CreateRunOptions()
• plot.OutputsModel()
• .GetFeatModel()