general: update supplier, bugfixing

- update supplierPanel to look like product and customer
- fix customerPanel and productPanel
- when all items were deleted, the panels crashed
RetailSystemSwingView: support SupplierPanel

- support new SupplierPanel
RandomDataGenerator: add method to clean users

- add extra method to clean users without affecting other data
Merge branch 'master' of ssh://github.com/d14123081/team4

Conflicts:
	Retail Storage System.db