Add option to make pages available only on one domain

- 2021년에 next 브랜치 적용을 목표로 작업했던 것 가져옴
- modules 테이블에 domain_srl을 추가하여 특정 도메인에서만 유효하도록 설정 가능
- site_srl 변수를 사용하던 곳 중 삭제할 수 있는 곳은 모두 삭제함

modules/module/lang/en.php

@@ -77,8 +77,7 @@ $lang->msg_cannot_delete_for_child = 'Cannot delete a category which has child c
 $lang->msg_limit_mid = 'Only alphanumeric can be used in the module name.';
 $lang->msg_extra_name_exists = 'Already registered field ID. Please input another name.';
 $lang->about_browser_title = 'It will be shown in the browser title. It will be also used in a RSS/Trackback.';
-$lang->about_mid = 'The module name will be used like http://address/?mid=ModuleName.
-(Only english alphabet letters, numbers and underscore can be used. The maximum length is 40.)';
+$lang->about_mid = 'The module name must begin with a Latin alphabet, and only consist of Latin alphabets, numerals, and underscores.';
 $lang->about_default = 'If checked, this module will be shown when users access the site without mid value (mid=NoValue).';
 $lang->about_module_category = 'It enables you to manage it through a module category.
  The URL for the module manager is <a href="./?module=admin&amp;act=dispModuleAdminCategory">Module category </a>.';