within dataset-subdaset check variable type consistency over time

[lucasmation]

based on the list with the imported data for all years ( #11 ) maybe create another list where each element is a data.frame containing the output of str(). I.e., the each row should represent a variable in the imported dataset, with the following columns: var_name, var_type, num_of_cathegories.

Then, Merge all the elements of the list for each subdataset into a single data frame, so we can see how vartype and num_of_cathegories merge should be on var_name. var_type and num_of_cathegories of each year should be rename before the merge to keep the year information in the column name Ex: for 2005: var_type, num_of_cathegories becomes var_type2005, num_of_cathegories2005