[RTL UI] Bidi-wrap filenames, paths, urls, metadata

bidi.lua:
- Revert "Alias everything to Bidi.nowrap() when in LTR UI,
  as using LTR isolates seems uneeded when already LTR" (part
  of a628714f) which was a wrong assumption: we need proper
  wrappers for all things paths. Enhance some of these wrappers.
- Fix GetText RTL wrapping which was losing empty lines and
  trailing \n.

- Wrap all paths, directories, filenames in the code with
  these wrappers.
- Wrap all book metadata (title, authors...) with BD.auto(),
  as it helps fixing some edge cases (like open/close quotation
  marks which are not considered as bracket types by FriBiDi).
  (Needed some minor logic changes in CoverBrowser.)

- Tweak hyphenation menu text
- Update forgotten SortWidget for UI mirroring
- KoptConfig: update "justification" index for RTL re-ordering,
  following the recent addition of the page_gap_height option.

frontend/apps/reader/modules/readermenu.lua

@@ -228,7 +228,7 @@ function ReaderMenu:setUpdateItemTable()
                 return _("Open previous document")
             end
             local path, file_name = util.splitFilePathName(previous_file) -- luacheck: no unused
-            return T(_("Previous: %1"), file_name)
+            return T(_("Previous: %1"), BD.filename(file_name))
         end,
         enabled_func = function()
             return self:getPreviousFile() ~= nil
@@ -239,7 +239,7 @@ function ReaderMenu:setUpdateItemTable()
         hold_callback = function()
             local previous_file = self:getPreviousFile()
             UIManager:show(ConfirmBox:new{
-                text = T(_("Would you like to open the previous document: %1?"), previous_file),
+                text = T(_("Would you like to open the previous document: %1?"), BD.filepath(previous_file)),
                 ok_text = _("OK"),
                 ok_callback = function()
                     self.ui:switchDocument(previous_file)