fixing receipt/gift receipt formatting in prep for adding date
receipt/gift receipt getting ready for date
receipt/gift receipt added date to print on receipt
added Javadoc for DiscountStrategy interface & the two pct strategies
added Javadoc for remaining discount strategies
added Javadoc for DataRetrievalStrategies & FakeDatabase classes
added Javadoc for Product & LineItem
added Javadoc for Customer, Receipt, GiftReceipt, and CashRegister
more Javadoc