When sending access granted/rejected emails we should also respect
custom emails set for groups/sub-groups

- Select notification email by walking up group/subgroup path
- Add settings UI to set group email notification address
- Add tests

A project in a group can have no explicit owners/masters,
in that case we fallbacks to the group's owners/masters.

Signed-off-by: Rémy Coutable <remy@rymai.me>

This reverts commit 13e37a3e.

+ Move 'Edit Project/Group' out of membership-related partial
+ Show the access request buttons only to logged-in users
+ Put the request access buttons out of in a more visible button
+ Improve the copy in the #remove_member_message helper

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>