新增了saleui中的三个类。目前进度：Sale类完成了除JPfunction相关的内容。好了我准备爬上去睡一觉。。。by 阿超
Merge branch 'master' of git@github.com:minusone13/InvoicingSystem.git

Conflicts:
	src/main/java/userui/TestFrame.java
Merge branch 'master' of git@github.com:minusone13/InvoicingSystem.git

Conflicts:
	src/main/java/userui/TestFrame.java
Merge branch 'master' of git@github.com:minusone13/InvoicingSystem.git
写完了JPfunctions。添加了图片。
Merge branch 'master' of git@github.com:minusone13/InvoicingSystem.git

Conflicts:
	src/main/java/userui/TestFrame.java