updated ProductTest
Updated InventoryTest
Updated CartTest
Created JUnit test case UserTest.
Created JUnit test case UserListTest.
Created JUnit test case PaymentValidatorTest.
Created JUnit test case DBManagerTestTest.
Created JUnit test case DBManagerTest.
Created JUnit test case CartSystemTest.
Merge branch 'seth' of https://github.com/jr-news/cop5339 into seth

Conflicts:
	database/Inventory.dat
Updated Javadoc comments in CartSystem
Updated Javadoc comments in DBManager
Updated Javadoc comments in Inventory
Updated Javadoc comments in Product
Updated Javadoc comments in ProductList
Updated Javadoc comments in PrunningIterator
Updated PrunningIteratorTest
Updated Javadoc comments in AbstractScreen
Updated Javadoc comments
Decorator Pattern UML diagram tweak