RAnEn::readObservations and RAnEn::readForecasts need updating

[Weiming-Hu]

Since Forecasts and Observations now can be a sub-group in a NetCDF file, these two functions need to be able to handle that situation.

A possible solution is to define a variable prefix.

  # Check if Observations is the root group
  # If it is the root group, no variable prefix is needed
  # If it is not the root group, the variable prefix should be "Observations/"
  # 
  var_prefix <- ''
  if (any(grepl("^Observations", names(nc$var)))) {
    var_prefix <- 'Observations/'
  }

[Weiming-Hu]

Resolved in 91c45350fc0c7eb53e27df617f25db3ab47d9e0c