[IMP] fields: split multi-purpose '_origin' into 'column' and 'inherited'

This makes it easier to determine when a field interfaces a column, and when it
implements an inherited field (with _inherits).
[IMP] fields: allow sorting on inherited field in list views
[FIX] account: fixed broken constraint (due to the passage to the new API) to ensure the same partner is present on journal items we try to reconcile partially. Fixes #2527
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64