[FIX] Model.load(): extra error checking while importing data

If any missing or partially incorrect values cause
an exception other than a psycopg2 error, we should
still catch it, rollback that record and report
the error, rather than letting bubble and fail
without any feedback to the user.

Fixes #1485
Merge branch '7.0' of https://github.com/odoo/odoo into 7.0-win32