update checkout, orderhistory
Merge remote-tracking branch 'origin/master'

Conflicts:
	OBG_System/BusinessLogic/DiscountBLO.cs
	OBG_System/DataAccess/DiscountDAO.cs
	OBG_System/OBG_System/Bin/BusinessLogic.dll
	OBG_System/OBG_System/Bin/BusinessLogic.pdb
	OBG_System/OBG_System/Bin/DataAccess.dll
	OBG_System/OBG_System/Bin/DataAccess.pdb