- and update views calling it

this is just me testing to see where the linebreak should be because I d
- `issuable_sort_option_overrides` has sort options that are only
  available by reversing the sorting.
- `issuable_reverse_sort_order_hash` maps sorting in one direction
  to the other, both ways.
- `issuable_sort_option_title` uses `issuable_sort_option_overrides` to
  get the correct title (so you see the same sort title no matter the
  direction we ordered in).
- `issuable_sort_direction_button` shows a button to reverse the
  sorting. It's disabled if the current sort is irreversible
  (like for Priority).