Project admin and project manager for company #4696

Would have been cleaner if

```python
NereidUser = Pool().get('nereid.user')

assert name in ('project_admins', 'project_managers')

if name == 'project_admins':
    permission = 'project.admin'
elif:
    permission = 'project.manager'

domain = [
    ('company', '=', self.id),
    ('permissions.value', '=', permission),
]

return map(int, NereidUser.search(domain))
```