name_to_code_mun: Retrieve municipalities' DIVIPOLA codes from names
Description
Retrieve municipalities' DIVIPOLA codes from their names. Since there are
municipalities with the same names in different departments, the input must
include two vectors: one for the departments and one for the municipalities
in said departments. If only one department is provided, it will try to
match all municipalities in the second vector inside that department.
Otherwise, the vectors must be the same length.