create "UpdateStock" function in DatabaseConnection.cs and it used in StockControl.cs file...

CheckQuantity function in databaseConnection.cs use to get the current Quantity of given Item
Merge branch 'Gayan' of https://github.com/Kasunucsc/MotorYardInv into Pubudu

Conflicts:
	Motor Yard/obj/Debug/Motor Yard.csproj.FileListAbsolute.txt