Add some TODO comments for cropcover, cropyield functions

src/crop/almass.jl

@@ -91,8 +91,8 @@ end
 croptype(cs::CropState) = cs.croptype
 cropname(cs::CropState) = cropname(croptype(cs))
 cropheight(cs::CropState) = cs.height
-cropcover(cs::CropState) = 0.0
-cropyield(cs::CropState) = 0.0
+cropcover(cs::CropState) = 0.0  # TODO: related to LAItotal, LAIgreen?
+cropyield(cs::CropState) = 0.0  # TODO: units? needs biomass?
 
 """
     Base.tryparse(type, str)

src/crop/simplecrop.jl

@@ -29,7 +29,7 @@ croptype(cs::CropState) = cs.croptype
 cropname(cs::CropState) = cropname(croptype(cs))
 cropheight(cs::CropState) = cs.height
 cropcover(cs::CropState) = 0.0
-cropyield(cs::CropState) = 0.0
+cropyield(cs::CropState) = 0.0  # TODO: units?
 
 
 """