增加了SalesListItem和PurchaseListItem

修改了Goods，数量不应当是商品的属性
Merge branch 'master' of https://github.com/WRKMNO4/System_Client

Conflicts:
	src/PO/GoodsPO.java
	src/PO/PurchaseReceiptPO.java
	src/PO/SalesReceiptPO.java
	src/VO/GoodsVO.java
	src/VO/PurchaseReceiptVO.java
	src/VO/SalesReceiptVO.java