[FIX] contract_sale_generation: it doesn't create sales (OCA#141)

* Change the method called in the view
* Complete the create_invoice method
* Bump version + authoring
* Correct bad call of method
  Small Documentation
* Add super call in python test
* FIX bad field names causing bad quantities in sale.order.line

product_contract/tests/test_sale_order.py

@@ -24,6 +24,7 @@ def tearDown(self):
         self.env['account.analytic.account']._revert_method(
             'create',
         )
+        super(TestSaleOrder, self).tearDown()
 
     def test_action_done(self):
         """ It should create a contract when the sale for a contract is set