[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/readerlink.lua

@@ -534,7 +534,7 @@ function ReaderLink:onGotoLink(link, neglect_current_location, allow_footnote_po
                 display_filename = display_filename .. anchor
             end
             UIManager:show(ConfirmBox:new{
-                text = T(_("Would you like to read this local document?\n\n%1\n"), display_filename),
+                text = T(_("Would you like to read this local document?\n\n%1\n"), BD.filepath(display_filename)),
                 ok_callback = function()
                     UIManager:scheduleIn(0.1, function()
                         self.ui:switchDocument(linked_filename)
@@ -543,7 +543,7 @@ function ReaderLink:onGotoLink(link, neglect_current_location, allow_footnote_po
             })
         else
             UIManager:show(InfoMessage:new{
-                text = T(_("Link to unsupported local file:\n%1"), link_url),
+                text = T(_("Link to unsupported local file:\n%1"), BD.url(link_url)),
             })
         end
         return true
@@ -551,7 +551,7 @@ function ReaderLink:onGotoLink(link, neglect_current_location, allow_footnote_po
 
     -- Not supported
     UIManager:show(InfoMessage:new{
-        text = T(_("Invalid or external link:\n%1"), link_url),
+        text = T(_("Invalid or external link:\n%1"), BD.url(link_url)),
         -- no timeout to allow user to type that link in his web browser
     })
     -- don't propagate, user will notice and tap elsewhere if he wants to change page
@@ -658,7 +658,7 @@ function ReaderLink:onGoToExternalLink(link_url)
             -- No external link handler
             return false
         end
-        text = T(_("External link:\n\n%1"), link_url)
+        text = T(_("External link:\n\n%1"), BD.url(link_url))
     end
 
     -- Add all alternative handlers buttons