check_field_structure

'check_field_structure': check the validity of the field struture representation consistant with the netcdf format
----------------------------------------------------------------------
 function [DataOut,errormsg]=check_field_structure(Data)

 OUTPUT:
  Data: structure reproducing the input structure Data, with the additional elements:
           with fields:

            .ListDimName: cell listing the names of the array dimensions
             .DimValue: array dimension values (Matlab vector with the same length as .ListDimName
            .VarDimIndex: cell containing the set of dimension indices (in list .ListDimName) for each variable of .ListVarName
            .VarDimName: cell containing a cell of dimension names (in list .ListDimName) for each variable of .ListVarName
 errormsg: error message which is not empty when the input structure does not have the right form

INPUT:
 Data:   structure containing 
         (optional) .ListGlobalAttribute: cell listing the names of the global attributes
                    .Att_1,Att_2... : values of the global attributes
         (requested)  .ListVarName: list of variable names to select (cell array of  char strings {'VarName1', 'VarName2',...} ) 
         (requested)  .VarDimName: list of dimension names for each element of .ListVarName (cell array of string cells)                         
         (requested) .Var1, .Var2....: variables (Matlab arrays) with names listed in .ListVarName