Add an access to Hyperlinks within worksheets.
!! NOTE: erx::Row object are now cached on demand, may have side effects on efficiency/memory consumption. !!
Add erx::Worksheet::get_range($range)
Add erx::Worksheet::get_link($range)
Add erx::Worksheet::follow_link($link)
Add erx::Worksheet::get_row($row_number)
Add erx::Row::get_cell($col_index)
Add erx::Row::clone()
Add erx::Cell::range()
Add erx::Cell::clone()