[FIX] account: fix unexpected invalidation of field account_invoice.reconciled

Problem: the field account_invoice.reconciled was invalidated by a workflow
signal sent from the compute method of the field. The purpose of the signal was
to re-open the invoice when the account move lines were no longer reconciled,
for instance after cancelling a reconciliation.

Solution: modify the workflow such that it makes an automatic transition from
'paid' to 're-open' when the condition 'not reconciled' is met. This works
because the field 'reconciled' is stored, and each recomputation forces a
reevaluation the workflow. The signal to re-open the invoice is thus no longer
necessary.
[FIX] mrp: Fix spelling error on 'manufacturing'

Changing .po files to avoid to retranslate existing terms.
Fixes #1328
Merge pull request #1581 from odoo-dev/8.0-fix-account-invoice-rco

[FIX] account: fix unexpected invalidation of field account_invoice.reconciled
[IMP] workflow: add sequence for ordering workflow transitions (split/join mode especially for XOR)

Makes ordering transitions easier and more deterministic.

(Rebase of #1564)
[FIX] hr_contract: count the number of contracts of an employee as superuser_id as this field is required in the form view. However no data is displayed, and no data about the contracts are leaked, so no security holes.