WorkflowTool.py: now converted workflow can have the same ID as old DCWorkflow, and old DCWorkflow will be moved to trash tool.

WorkflowTool.py: add variable's expression as getReference iff when variable is action and it has a default_expr.

WorkflowTool.py: Enhance doActionFor compatibility at the case which both workflow are assigned to the same object type AND workflow has a prior initial letter to DC workflow.

WorkflowTool.py: add workflow_script reference in conversion codes; add a chains_by_type repair script related function.

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

ERP5WorkflowTool.py: add bootstrap function to migrate the workflow tool conditionally-autoomatically.