Overrides of _notify_get_groups are used to add some buttons in notification
emails and control the display of "Access document" button. This commit
cleans some overrides :
* accounting: portal users that are not the customer have no access to the
invoice and should not have the access button;
* project: remove unnecessary override on project model and consider portal
users have access to the document through customer portal;
* sale: portal users that are not the customer have no access to the sale
order and should not have the access button;
* website_blog: display access button to everyone only if the post is
published; otherwise keep standard behavior;
* website_forum: display access button to everyone only if the post
has not been closed or deactivated; otherwise keep standard behavior;
* website_slides: display access button to everyone only if the slides
has been published; otherwise keep standard behavior;
Thibault Delavallée
86350c56ff