Removed rsort functions and published the one having the 'dir' argument.
Use 'dir' (1, -1) instead of 'inv' (y/n) in iterators.

For consistency with sorting functions.
Added a 'dir' to struct boro_mr (used only in 'sort' and 'sort_by' by now).
boro_mr() now also uses the 'dir' parameter to iterate.