This reverts commit 5a586f364c5d2b866d6a074eff7996f05585b7d5

This reverts merge request !3191

Support Golang subpackage fetching

Closes #13805

See merge request !3191

Removed User#project_relations

This is to make things more compatible with EE so merging is easier.

cc @dzaporozhets 

See merge request !3192

GitLab EE adds an extra relation that selects a "project_id" column
instead of an "id" column, making it very hard for this method to be
re-used in EE. Since using User#authorized_groups in
ProjectsFinder#all_groups apparently has no performance impact we can
just use it and keep everything compatible with EE.

Disallow blank (non-null) values for a Note's `line_code` attribute

It's unclear how these blank values got added, but GitLab.com had a few:

```
irb(main):002:0> Note.where("line_code IS NOT NULL AND line_code = ''").count
=> 439
```

We've added a migration to convert any existing records to use a NULL
value when blank, and updated Note to set blank values to nil before
validation.

See merge request !3118

fix token issue - timing attack

Updates token comparisons to use a secure version instead of `==`

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/13617

See merge request !3062

# Conflicts:
#	app/helpers/application_helper.rb

Fix responsive bug top navigation

Hi,

I have found and fixed a minor layout bug (responsive)

This is the situation before the fix:
![before](/uploads/55bf61a64fb49a763c5f8381bf46d390/before.png)

And this is the situation after the fix:
![after](/uploads/33ba091156d404e52c41f134121c59f0/after.png)

See merge request !3190