[ADD] website portal module to display portal in website + user groups: ...

...display website menu based on user groups

- Task: https://www.odoo.com/web#id=8568&view_type=form&model=project.task
- Pad: https://pad.odoo.com/p/r.C1Ps0gZXGqJwbhh8
I suppose the code could be cleaned here : 
- avoid using long(), this make no sense here
- you could simplify the use of limit and offset in a one-liner
- please try to lessen the number of if / else / if, this is a good exercise of avoiding writing 20 lines were half is necessary.