Fix S4 classes argument documentation

[TheoPannetier]

From R CMD CHECK:

* checking for code/documentation mismatches ... WARNING
Codoc mismatches from documentation object 'ArtificialLandscape':
ArtificialLandscape
  Code: function(...)
  Docs: function(propSuit = 0.5, K_or_DensDep = 10, Resolution = 100,
                 dimX = 65, dimY = 65, fractal = FALSE, hurst,
                 continuous = FALSE, minPct, maxPct)
  Argument names in code not in docs:
    ...
  Argument names in docs not in code:
    propSuit K_or_DensDep Resolution dimX dimY fractal hurst continuous
    minPct maxPct
  Mismatches in argument names:
    Position: 1 Code: ... Docs: propSuit

I'm not sure why the arguments are replaced by ... in the code, nor of what's the correct way to document classes.
Maybe this R packages section can help?