MenuSorter: initial implementation

* Menus are now sanely configurable
* Custom separator placement for clearer menus

frontend/apps/reader/modules/readerhighlight.lua

@@ -66,10 +66,10 @@ end
 
 function ReaderHighlight:addToMainMenu(tab_item_table)
     -- insert table to main reader menu
-    table.insert(tab_item_table.typeset, {
+    self.ui.menu.menu_items["highlight_options"] = {
         text = _("Highlight options"),
         sub_item_table = self:genHighlightDrawerMenu(),
-    })
+    }
 end
 
 local highlight_style = {