Various changes to sorting (#4067)

Don't consider sidecar file when sorting by access time.
Rename 'sort by title' to 'sort by filename':
This is in accordance with the actual function of the code, which
uses filename rather than title as specified in file metadata.

frontend/apps/filemanager/filemanager.lua

@@ -742,7 +742,7 @@ end
 function FileManager:getSortingMenuTable()
     local fm = self
     local collates = {
-        strcoll = {_("title"), _("Sort by title")},
+        strcoll = {_("filename"), _("Sort by filename")},
         access = {_("date read"), _("Sort by last read date")},
         change = {_("date added"), _("Sort by date added")},
         modification = {_("date modified"), _("Sort by date modified")},

frontend/ui/widget/filechooser.lua

@@ -126,12 +126,6 @@ function FileChooser:genItemTableFromPath(path)
         end
     elseif self.collate == "access" then
         sorting = function(a, b)
-            if DocSettings:hasSidecarFile(a.fullpath) and not DocSettings:hasSidecarFile(b.fullpath) then
-                return true
-            end
-            if not DocSettings:hasSidecarFile(a.fullpath) and DocSettings:hasSidecarFile(b.fullpath) then
-                return false
-            end
             return a.attr.access > b.attr.access
         end
     elseif self.collate == "modification" then