[IMP] expression.py: add a check to forbid records in domains

Records in domains cause a "maximum recursion depth exceeded" error when
converted to SQL. Simply add a test to show a better error message.
[ADD] QWeb2: add support for operation='attributes' in a t-extend

Same syntax as server's position='attributes' on view inheritance
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64