[7.0] Add account journal period close

Add account_journal_period_close module

This module allows fine grained control of period closing.
Each journal can be closed independently for any period
(using buttons on the fiscal period view).

A common use case is letting accountants close the sale
and purchase journals when the VAT declaration is done for
a given period, while leaving the miscellaneous journal open.

From a technical standpoint, the module leverages the
account.journal.period model that is present in Odoo core.