budget: allow Categories in node budget variation relation field

We have been using scripts returning categories but it was
missing in the relation field.

bt5/erp5_budget/SkinTemplateItem/portal_skins/erp5_budget/NodeBudgetVariation_view/my_aggregate_title_list.xml

@@ -248,6 +248,10 @@
                     <key> <string>container_getter_id</string> </key>
                     <value> <string></string> </value>
                 </item>
+                <item>
+                    <key> <string>context_getter_id</string> </key>
+                    <value> <string></string> </value>
+                </item>
                 <item>
                     <key> <string>css_class</string> </key>
                     <value> <string></string> </value>
@@ -300,6 +304,10 @@
                     <key> <string>hidden</string> </key>
                     <value> <string></string> </value>
                 </item>
+                <item>
+                    <key> <string>input_type</string> </key>
+                    <value> <string></string> </value>
+                </item>
                 <item>
                     <key> <string>items</string> </key>
                     <value> <string></string> </value>
@@ -603,7 +611,7 @@
       <dictionary>
         <item>
             <key> <string>_text</string> </key>
-            <value> <string>python: [(x, x) for x in (here.getPortalNodeTypeList() + here.getPortalPaymentNodeTypeList() + here.getPortalResourceTypeList() + here.getPortalProjectTypeList())]</string> </value>
+            <value> <string>python: [(x, x) for x in (here.getPortalNodeTypeList() + here.getPortalPaymentNodeTypeList() + here.getPortalResourceTypeList() + here.getPortalProjectTypeList() + (\'Category\',))]</string> </value>
         </item>
       </dictionary>
     </pickle>