document all functions with "roxygen2"

[mrustl]

see example: https://github.com/KWB-R/urbanAnnualRunoff/blob/dev/R/imgClass.R

details:
https://cran.r-project.org/web/packages/roxygen2/vignettes/roxygen2.html
https://r-pkgs.org/man.html?q=roxygen#man

[mrustl]

@robetatis please better document the remaining functions which are of importance, e.g.:

[mrustl]

So no more progress on that @robetatis I suppose?

But the only adaptations I need to make are updating the calculations for new climate data right? (precipitation, evapotranspiration using satellite data).