Make email notifications per project/group

Email notifications should be eligible per group or project

When belonging to multiple groups and projects it is useful to use an specific email address for the project or the group. Not only because of self organising the work but also because different groups could belong to different organizations. Cross receiving emails from one group/organizarion in the other's email makes the work complicated.

Proposal

Add the option of choosing, among the email addresses of one's account, which receives notifications for every project, defaulting in the default notification email if not set.

References

This issue occurs at the Enterprise Edition used by gitlab.com site, where one account could contribute to multiple OpenSource projects and for some of them, I have an email from that organization.