erp5_trade: REVIEW add Inventory Offset Line and Cell to inventory movement group

I am unsure if they should not instead be in the delivery movement group, that way we might be able to discard my change to ERP5Site and get rid completely of this inventory movement thing.

bt5/erp5_trade/PortalTypeTemplateItem/portal_types/Inventory%20Offset%20Cell.xml

@@ -20,6 +20,14 @@
               <none/>
             </value>
         </item>
+        <item>
+            <key> <string>group_list</string> </key>
+            <value>
+              <tuple>
+                <string>inventory_movement</string>
+              </tuple>
+            </value>
+        </item>
         <item>
             <key> <string>id</string> </key>
             <value> <string>Inventory Offset Cell</string> </value>

bt5/erp5_trade/PortalTypeTemplateItem/portal_types/Inventory%20Offset%20Line.xml

@@ -20,6 +20,14 @@
               <none/>
             </value>
         </item>
+        <item>
+            <key> <string>group_list</string> </key>
+            <value>
+              <tuple>
+                <string>inventory_movement</string>
+              </tuple>
+            </value>
+        </item>
         <item>
             <key> <string>id</string> </key>
             <value> <string>Inventory Offset Line</string> </value>