设计一个用于人事管理的People（人员）类。

考虑到通用性，这里只抽象出所有类型人员都具有的属性：

number（编号）、sex（性别）、birthday（出生日期）、id（身份证号）等。

其中“出生日期”声明为一个“日期”类内嵌子对象。用成员函数实现对人员信息的录入和显示。

要求至少包括：构造函数和析构函数、拷贝构造函数-People (staff) designed for personnel management class. Taking into account the versatility, abstract all types have attributes: number (ID), sex (gender), birthday (date of birth), id (ID number). " Date of Birth"　is declared as a " date"　class embedded sub-objects. Member function entry and display of personnel information. Requirements include at least: constructor and destructor, copy constructor