WorkflowTool.py: repair the Expression of the converted workflow variable; finish the methods to modify chain_by_type. Now the reassignment of the converted workflows works

erp5_workflow: visualise state's assigned permission role by showing a stupid text field. Matrixbox doesn't show the real assignment, but solution unknow.

erp5_workflow: add conversion form_dialog in portal_workflow to allow convert selected dc workflows.

patches/WorkflowTool.py: Workflow Tool migration now happening after install erp5_workflow template.