[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/readerui.lua

@@ -4,6 +4,7 @@ ReaderUI is an abstraction for a reader interface.
 It works using data gathered from a document interface.
 ]]--
 
+local BD = require("ui/bidi")
 local Cache = require("cache")
 local ConfirmBox = require("ui/widget/confirmbox")
 local Device = require("device")
@@ -448,14 +449,14 @@ function ReaderUI:showReader(file, provider)
 
     if lfs.attributes(file, "mode") ~= "file" then
         UIManager:show(InfoMessage:new{
-             text = T(_("File '%1' does not exist."), file)
+             text = T(_("File '%1' does not exist."), BD.filepath(file))
         })
         return
     end
 
     if not DocumentRegistry:hasProvider(file) and provider == nil then
         UIManager:show(InfoMessage:new{
-            text = T(_("File '%1' is not supported."), file)
+            text = T(_("File '%1' is not supported."), BD.filepath(file))
         })
         self:showFileManager(file)
         return
@@ -471,7 +472,7 @@ function ReaderUI:showReader(file, provider)
             (provider.provider == "mupdf" and type(bookmarks[1].page) == "string")) then
                 UIManager:show(ConfirmBox:new{
                     text = T(_("The document '%1' with bookmarks or highlights was previously opened with a different engine. To prevent issues, bookmarks need to be deleted before continuing."),
-                        file),
+                        BD.filepath(file)),
                     ok_text = _("Delete"),
                     ok_callback = function()
                         doc_settings:delSetting("bookmarks")
@@ -488,7 +489,7 @@ end
 
 function ReaderUI:showReaderCoroutine(file, provider)
     UIManager:show(InfoMessage:new{
-        text = T(_("Opening file '%1'."), file),
+        text = T(_("Opening file '%1'."), BD.filepath(file)),
         timeout = 0.0,
     })
     -- doShowReader might block for a long time, so force repaint here