Fixed fatal error in sale when anything but an integer is entered
Now a error box will display if the the value is greater then the stock 
and if tanything else but an integer is added.
Supplier table now refreshes straight away
Changed SaleMainPanel so that previous salesare erased from the text
area when new sale is made

Merge branch 'master' into christine

Conflicts:
	orders.ser
	sales.ser
	stocks.ser