Added methods for paying and checking the payment status of a BillItem.
Added setTab() to RoomBooking and implemented it.
Implemented makePaymentForRoomBooking, which will hopefully not be
broken after the next merge.
Merge remote-tracking branch 'origin/master' into checkout2

Conflicts:
	se.chalmers.TDA593.Book-a-Hobbit/src/hobbit/model/impl/BillItemImpl.java
Added updateTab() to booking-classes
Implemented makePaymentForMasterBooking
Merge branch 'master' into checkout2

Conflicts:
	se.chalmers.TDA593.Book-a-Hobbit/src/hobbit/model/AGenericBooking.java
	se.chalmers.TDA593.Book-a-Hobbit/src/hobbit/model/impl/BillItemImpl.java
	se.chalmers.TDA593.Book-a-Hobbit/src/hobbit/model/impl/PaymentControllerImpl.java
Merge branch 'master' into checkout2

Conflicts:
	se.chalmers.TDA593.Book-a-Hobbit/src/hobbit/model/impl/PaymentControllerImpl.java
Removed old and redundant version of isBillSettled()