Draft: Riv-temp: distributed parameters

Parameters for the river temperature module can now be given as distributed values for each month with NetCDF files.

There are new namelist entries in &config_riv_temp with file paths for each distributed parameter per domain:

  file_albedo_water(1) = "test_domain/input/optional_data/albedo_water.nc"
  file_pt_a_water(1) = ""
  file_emissivity_water(1) = ""
  file_turb_heat_ex_coeff(1) = ""
  file_albedo_water(2) = "test_domain_2/input/optional_data/albedo_water2.nc"
  file_pt_a_water(2) = ""
  file_emissivity_water(2) = ""
  file_turb_heat_ex_coeff(2) = ""

If one parameter is given per file for one domain, all domains need to have this parameter as a distributed one. (Either all domains use this parameter as constant or all as distributed) If the file path is empty (""), then the constant namelist entries will be used as before (default, the file_* namelist entries can be omitted).

Each file needs to have a variable with the respective parameter name ("albedo_water", "pt_a_water", "emissivity_water", "turb_heat_ex_coeff"). Note: They can be in the same file.

Dimensions need to be (month, y, x):

$ ncdump -h albedo_water.nc 
netcdf albedo_water {
dimensions:
        month = 12 ;
        y = 9 ;
        x = 6 ;
variables:
        double albedo_water(month, y, x) ;