More import script updates and fixes, better import_history tracking

inventory-server/db/schema.sql

@@ -118,6 +118,7 @@ CREATE TABLE IF NOT EXISTS orders (
     status VARCHAR(20) DEFAULT 'pending',
     canceled TINYINT(1) DEFAULT 0,
     PRIMARY KEY (id),
+    UNIQUE KEY unique_order_line (order_number, pid),
     KEY order_number (order_number),
     KEY pid (pid),
     KEY customer (customer),