[IMP] website_quote:add checkbox into quote template to add empty templa...

...te in quotation and implement back button into edit quote template

- Task: https://www.odoo.com/web?#id=9298&view_type=form&model=project.task&menu_id=3942&action=327
- Pad: https://pad.odoo.com/p/r.vr8kETxQIzMBoUZA