[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/cloudstorage/dropbox.lua

@@ -1,3 +1,4 @@
+local BD = require("ui/bidi")
 local ConfirmBox = require("ui/widget/confirmbox")
 local DocumentRegistry = require("document/documentregistry")
 local DropBoxApi = require("apps/cloudstorage/dropboxapi")
@@ -26,12 +27,12 @@ function DropBox:downloadFile(item, password, path, close)
         local __, filename = util.splitFilePathName(path)
         if G_reader_settings:isTrue("show_unsupported") and not DocumentRegistry:hasProvider(filename) then
             UIManager:show(InfoMessage:new{
-                text = T(_("File saved to:\n%1"), path),
+                text = T(_("File saved to:\n%1"), BD.filename(path)),
             })
         else
             UIManager:show(ConfirmBox:new{
                 text = T(_("File saved to:\n%1\nWould you like to read the downloaded book now?"),
-                    path),
+                    BD.filepath(path)),
                 ok_callback = function()
                     close()
                     ReaderUI:showReader(path)
@@ -40,7 +41,7 @@ function DropBox:downloadFile(item, password, path, close)
         end
     else
         UIManager:show(InfoMessage:new{
-            text = T(_("Could not save file to:\n%1"), path),
+            text = T(_("Could not save file to:\n%1"), BD.filepath(path)),
             timeout = 3,
         })
     end