trade: allow using value 0 for the quantity in fast inputs

0 is a valid value. So instead of showing by default 0.0 for all quantities and forcing users to set
something different than 0, now by default the quantity is empty, and user is forced to something
something different from empty.

bt5/erp5_item/SkinTemplateItem/portal_skins/erp5_item_trade/Base_viewTradeFieldLibrary/my_dialog_mode_listbox_quantity.xml

@@ -10,10 +10,8 @@
             <key> <string>delegated_list</string> </key>
             <value>
               <list>
-                <string>description</string>
                 <string>editable</string>
                 <string>external_validator</string>
-                <string>title</string>
               </list>
             </value>
         </item>
@@ -63,10 +61,6 @@
             <key> <string>tales</string> </key>
             <value>
               <dictionary>
-                <item>
-                    <key> <string>description</string> </key>
-                    <value> <string></string> </value>
-                </item>
                 <item>
                     <key> <string>editable</string> </key>
                     <value>
@@ -89,10 +83,6 @@
                     <key> <string>target</string> </key>
                     <value> <string></string> </value>
                 </item>
-                <item>
-                    <key> <string>title</string> </key>
-                    <value> <string></string> </value>
-                </item>
               </dictionary>
             </value>
         </item>
@@ -100,10 +90,6 @@
             <key> <string>values</string> </key>
             <value>
               <dictionary>
-                <item>
-                    <key> <string>description</string> </key>
-                    <value> <string>Default Quantity of a resource in ERP5. It can be a product or it can be time quantity like hours or minutes for example. Quantity can be found in almost every business field of ERP5 and will always have this meaning, unless the term is different or precise, such as Priced Quantity for example.</string> </value>
-                </item>
                 <item>
                     <key> <string>editable</string> </key>
                     <value> <int>1</int> </value>
@@ -116,20 +102,16 @@
                 </item>
                 <item>
                     <key> <string>field_id</string> </key>
-                    <value> <string>my_float_field</string> </value>
+                    <value> <string>my_dialog_mode_listbox_quantity</string> </value>
                 </item>
                 <item>
                     <key> <string>form_id</string> </key>
-                    <value> <string>Base_viewFieldLibrary</string> </value>
+                    <value> <string>erp5_trade/Base_viewTradeFieldLibrary</string> </value>
                 </item>
                 <item>
                     <key> <string>target</string> </key>
                     <value> <string>Click to edit the target</string> </value>
                 </item>
-                <item>
-                    <key> <string>title</string> </key>
-                    <value> <string>Quantity</string> </value>
-                </item>
               </dictionary>
             </value>
         </item>

bt5/erp5_item/SkinTemplateItem/portal_skins/erp5_item_trade/DeliveryLine_validateItemCreationDialogEditableField.py

-if not editor and (
+if editor in (None, '') and (
      request.get('field_listbox_title_%s' % request.cell.uid) or
      request.get('field_listbox_reference_%s' % request.cell.uid)):
   return False

bt5/erp5_trade/SkinTemplateItem/portal_skins/erp5_trade/Base_viewTradeFieldLibrary/my_dialog_mode_listbox_quantity.xml

@@ -10,6 +10,7 @@
             <key> <string>delegated_list</string> </key>
             <value>
               <list>
+                <string>default</string>
                 <string>editable</string>
               </list>
             </value>
@@ -53,11 +54,17 @@
             <value>
               <dictionary>
                 <item>
-                    <key> <string>editable</string> </key>
+                    <key> <string>default</string> </key>
                     <value>
                       <persistent> <string encoding="base64">AAAAAAAAAAI=</string> </persistent>
                     </value>
                 </item>
+                <item>
+                    <key> <string>editable</string> </key>
+                    <value>
+                      <persistent> <string encoding="base64">AAAAAAAAAAM=</string> </persistent>
+                    </value>
+                </item>
                 <item>
                     <key> <string>field_id</string> </key>
                     <value> <string></string> </value>
@@ -77,6 +84,10 @@
             <key> <string>values</string> </key>
             <value>
               <dictionary>
+                <item>
+                    <key> <string>default</string> </key>
+                    <value> <string></string> </value>
+                </item>
                 <item>
                     <key> <string>editable</string> </key>
                     <value> <int>1</int> </value>
@@ -100,6 +111,19 @@
     </pickle>
   </record>
   <record id="2" aka="AAAAAAAAAAI=">
+    <pickle>
+      <global name="TALESMethod" module="Products.Formulator.TALESField"/>
+    </pickle>
+    <pickle>
+      <dictionary>
+        <item>
+            <key> <string>_text</string> </key>
+            <value> <string>python: cell.getQuantity(None)</string> </value>
+        </item>
+      </dictionary>
+    </pickle>
+  </record>
+  <record id="3" aka="AAAAAAAAAAM=">
     <pickle>
       <global name="TALESMethod" module="Products.Formulator.TALESField"/>
     </pickle>

bt5/erp5_trade/SkinTemplateItem/portal_skins/erp5_trade/Delivery_viewDeliveryFastInputDialog/listbox_quantity.xml

@@ -15,6 +15,12 @@
               </list>
             </value>
         </item>
+        <item>
+            <key> <string>delegated_message_list</string> </key>
+            <value>
+              <list/>
+            </value>
+        </item>
         <item>
             <key> <string>id</string> </key>
             <value> <string>listbox_quantity</string> </value>
@@ -22,12 +28,7 @@
         <item>
             <key> <string>message_values</string> </key>
             <value>
-              <dictionary>
-                <item>
-                    <key> <string>external_validator_failed</string> </key>
-                    <value> <string>The input failed the external validator.</string> </value>
-                </item>
-              </dictionary>
+              <dictionary/>
             </value>
         </item>
         <item>
@@ -53,6 +54,10 @@
             <key> <string>tales</string> </key>
             <value>
               <dictionary>
+                <item>
+                    <key> <string>editable</string> </key>
+                    <value> <string></string> </value>
+                </item>
                 <item>
                     <key> <string>enabled</string> </key>
                     <value> <string></string> </value>