[ADD] slides gallery module

- Task: https://www.odoo.com/web?#id=9093&view_type=form&model=project.task
- Pad: https://pad.odoo.com/p/r.QlQTvBv6mCcMrK4B
render_attribute should return utf-8 encoded string.
when try to eval att with unicode string it will generate  QWebException: 'ascii' codec can't decode byte 0xc3 in position 29: ordinal not in range(128)