Util: Migrate func/string.php::HtmlEncode()

To: Util\StringUtil::encodeHtml()
Util: Migrate func/string.php::JsonEncodeHex()

To: Util\StringUtil::jsonEncodeHex()
Util: Migrate func/string.php::JsonEncodeUnicode()

To: Util\StringUtil::jsonEncodeUnicode()
Util: Move json relate method to class Util\Json
Util: Optimize duplicate string check and replace code
Util: Migrate func/string.php::RandomString()

To: Util\StringUtil::random()
Mis: Migrate func/string.php::OrgCodeGen()

To: Mis\OrgCode::gen()
Mis: Add method OrgCode::validate()