เพิ่มตัว unittest
  แก้ไข LoginManager
  แก้ไข Servlet

 Changes to be committed:
	modified:   ROOT/src/member_system/LoginManager.java
	modified:   ROOT/src/member_system/User.java
	modified:   ROOT/src/servlet/LoginServlet.java
	new file:   ROOT/src/unittest/TestLoginManager.java
	renamed:    ROOT/src/unittest/UnitTest.java -> ROOT/src/unittest/TestRegisterManager.java