[REVERT] web: fixed css of hidden input file: could not click on add attachments anymore

This reverts commit 4e32b9f6f32eea0e4a5bb9d83c5c5f45f775f799.
[FIX] osv/fields.py: enable argument 'obj' in property fields

Fixes #1719
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64