modules: add m-i18n

Add simple gettext i18n module.

Add Lua script API functions I18n.gettext, I18n.ngettext.

modules/module-lua-scripting/api/api.lua

@@ -186,6 +186,29 @@ local Feature = {
   },
 }
 
+local I18n = {
+  gettext = function (msgid)
+    local i18n = WpPlugin.find("i18n")
+    if i18n then
+      return i18n:call("gettext", msgid)
+    else
+      return msgid
+    end
+  end,
+  ngettext = function (msgid, msgid_plural, n)
+    local i18n = WpPlugin.find("i18n")
+    if i18n then
+      return i18n:call("ngettext", msgid, msgid_plural, n)
+    else
+      if n == 1 then
+        return msgid
+      else
+        return msgid_plural
+      end
+    end
+  end
+}
+
 SANDBOX_EXPORT = {
   Debug = Debug,
   Id = Id,
@@ -209,4 +232,5 @@ SANDBOX_EXPORT = {
   State = WpState_new,
   LocalModule = WpImplModule_new,
   ImplMetadata = WpImplMetadata_new,
+  I18n = I18n
 }