Only show group member roles if explicitly requested
This very simply fixes an EE problem, but I made the change here so it's less prone to errors from merges.
In EE, prior to this change, group member roles were shown in project member list when a project is shared with a group. This is bad because the project explicitly shares with the group and sets a 'max access' level. If the max access level is 'developer' the project owner doesn't want to see 'Owner' in the group roles because it will confuse them. I verified that permissions are really being honored here, it was just an error in the view. You can see in https://gitlab.com/gitlab-org/gitlab-ee/blob/master/app/views/projects/project_members/_shared_group_members.html.haml#L18 where this was how it was intended to be. Likely a CE-EE merge introduced this bug. That's why I made the boolean required in CE even though this is for EE.
## Before

## After

See merge request !3044
Don't show "Welcome to GitLab" when the search didn't return any projects
Fixes#13785. /cc @pixdrift
### Before

### After

See merge request !3059
Fix permissions for deprecated CI build status badge
This fixes permissions for deprecated status badge, being unavailable even if project is public.
Closes#13324
See merge request !3030
The controller was actually changed to not respond to AJAX but the
deletion button in the index.html was still using AJAX. There is no need
for AJAX when deleting a tag since it's a very rare use-case. KISS.
Fixes#13781
Fix issue with overlap of sidebar links.
Thanks @iamphill for the help with this one.

cc @iamphill @alfredo1 @dzaporozhets @rymai
See merge request !3043
Properly check for a pre-existing error in `User#namespace_uniq`
Rails adds an empty error to the Errors object even if you just call
`#[]` on it:
```
[1] pry(main)> u = User.last
[2] pry(main)> u.errors.keys
=> []
[3] pry(main)> u.errors[:username].present?
=> false
[4] pry(main)> u.errors.keys
=> [:username]
```
See merge request !3017
Don't show any "2FA required" message if it's not actually required
Prior, if the user had enabled and then disabled 2FA, they would be
shown a "You must enable Two-factor Authentication for your account."
message when going back to re-activate it, even if 2FA enforcement was
disabled.
See merge request !3014
Changed # to ! on merge requests on activity view
Closes#9082

See merge request !2938