Purpose:Store invoices and provide method to send to customers.

1.1Invoice Add
Purpose:Add invoices, listing open orders
Features:1. list open orders in multiable select
2. choose customer by currently selected customer, this is selected from customers list (unchangable, only by choosing customer in customer list)
3. choose sales person base on currently logged in user (selectable to give credit to other user)
4. Changable total, for deposits
5. Invoices based off of other invoices, require more payment
6. quick invoice, based off one order