simulation: identify the trade model path used for generating a simulation movement

A business process can define several trade model path for a single trade phase.
This will generate several simulation movement per rule input simulation movement.

When reexpanding a simulation tree, we have to do matching between generated
movement and existing simulation movements. Up to now, we do indirect matching
by looking at property that would be updated by trade model path (like source
or destination). But this indirect way is inconvenient and does not work as
expected when one of the matching property is changed.

It would be more convenient and more reliable to check directly from which
trade model path comes a simulation movement.

As an exemple, this is particular useful in the case of accounting, where in the
invoice transaction rule we usually generate an "accounting+" and an "accounting-"
movement through two distincts trade model path.

product/ERP5/Document/BusinessProcess.py

@@ -774,6 +774,12 @@ class BusinessProcess(Path, XMLObject):
       if value:
         property_dict[base_category] = value
 
+    # Allow to identify a trade model path by it's reference for possibly doing
+    # matching in simulation
+    reference = trade_model_path.getReference()
+    if reference:
+      property_dict['trade_model_path_reference'] = reference
+
     # Amount quantities - XXX-JPS maybe we should consider handling unit conversions here
     # and specifying units
     if trade_model_path.getQuantity():