Billogram + Heartland Integration

Keep Billogram and Heartland aligned: when finance events happen in one, update the other automatically.

Example: when Billogram's "Watch Billograms/Invoices" fires, WEXTL can "Add Item to a Purchase Order" in Heartland. Billogram has 3 triggers (including Watch Billograms/Invoices, Watch Customers, and Watch Items); Heartland has 50 actions (including Add Item to a Purchase Order, Add Item to a Receipt, and Add Item to a Return).