Changed the type of fields.date_order on purhcase.order object from date to datetime
[FIX] website_forum: fixed issue with user vote badly taken into account when upvoting / downvoting + crash due to wrong field name. Backport of Leonardo Donelli PR for master.
Merge pull request #1000 from odoo-dev/8.0-po-as-datetime-qdp

Changed fields.date_order on purchase.order from date to datetime