[REF] account: replace workflow by python code

addons/account/__openerp__.py

addons/account/demo/account_invoice_demo.yml

addons/account/models/account_invoice.py

addons/account/tests/test_account_customer_invoice.py

addons/account/tests/test_account_supplier_invoice.py

addons/account/tests/test_bank_statement_reconciliation.py

addons/account/tests/test_payment.py

addons/account/tests/test_reconciliation.py

addons/account/views/account_invoice_view.xml

addons/account/views/account_invoice_workflow.xml

addons/account/views/account_unit_test.xml

addons/account/wizard/account_invoice_refund.py

addons/account/wizard/account_invoice_state.py

addons/account_cancel/views/account_views.xml

addons/delivery/tests/test_delivery_stock_move.py

addons/membership/tests/test_membership.py

addons/point_of_sale/models/pos_order.py

addons/sale/models/account_invoice.py

addons/sale/tests/test_sale_order.py

addons/sale_stock/tests/test_sale_stock.py