[imp]Project:Improve the usability in project stage form view and projec...

...t form view.

Task: https://www.odoo.com/web#id=10838&view_type=form&model=project.task&menu_id=3942&action=327
Pad: https://pad.odoo.com/p/r.hi9Pu2KGw5HZYcXp
Invisible when there is value ?, as per spec, "as and field" should be hidden when there is no use_tasks, do not hide label