easier strings to translate

frontend/apps/reader/modules/readerfont.lua

@@ -220,7 +220,7 @@ end
 function ReaderFont:makeDefault(face)
     if face then
         UIManager:show(ConfirmBox:new{
-            text = _("Set default font \"")..face.."\"?",
+            text = _("Set default font to ")..face.."?",
             ok_callback = function()
                 G_reader_settings:saveSetting("cre_font", face)
             end,

frontend/apps/reader/modules/readerzooming.lua

@@ -335,7 +335,7 @@ end
 
 function ReaderZooming:makeDefault(zoom_mode)
     UIManager:show(ConfirmBox:new{
-        text = _("Set default zoom mode to \"")..zoom_mode.."\"?",
+        text = _("Set default zoom mode to ")..zoom_mode.."?",
         ok_callback = function()
             G_reader_settings:saveSetting("zoom_mode", zoom_mode)
         end,

frontend/ui/widget/configdialog.lua

@@ -577,7 +577,7 @@ end
 
 function ConfigDialog:onMakeDefault(name, name_text, values, labels, position)
     UIManager:show(ConfirmBox:new{
-        text = _("Set default ")..(name_text or "").." to "..labels[position].."?",
+        text = _("Set default ")..(name_text or "").._(" to ")..labels[position].."?",
         ok_callback = function()
             local name = self.config_options.prefix.."_"..name
             G_reader_settings:saveSetting(name, values[position])