!!!IMPORTANT CHANGE!!!
	both the mail and parcel constructors have changed! now the cost must
be included as a parameter.
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Have added 2 methods to get the total sales from the mailevents. first
one "getTotalSales()" gets ALL sales. and the other
"getTotalSalesBetweenDates(String date1, String date2)" does what it
says it does. This means that changes to the mailevents database was
made, that being the tag <cost> was added. Mail and Parcel now return
cost from it's brand spanking new cost field.