add 'portal_type_workflow_chain/' to the type of the workflow_chain_type as it is added also in _importFiles (https://lab.nexedi.com/nexedi/erp5/blob/master/product/ERP5/Document/BusinessTemplate.py#L2693).

@romain spotted this issue here https://lab.nexedi.com/nexedi/erp5/blame/master/bt5/erp5_web_renderjs_ui/PortalTypeWorkflowChainTemplateItem/workflow_chain_type.xml

Since migration only imported and exported without building, in the file we have now:

<type>portal_type_workflow_chain/Web Script</type> 

If someone uses git tab though, BT is built and 'portal_type_workflow_chain/' is eliminated and there is unexpected diff. This commit adds 'portal_type_workflow_chain/' also in build. I do not think I see something different in portal_workflow and no unexpected test failures (https://nexedi.erp5.net/test_result_module/20160314-2D78E1FA). Other option might be to remove it from L2693 and re-migrate to updated those files. @seb @jerome do you have any opinion in this?