[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
redirect should be decided by controller, not a model. 
In model, we should check unique slide or not and controller should be decided what to do after get result from model.