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
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]
```
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.
Prior, if the user enabled 2FA, then disabled it and came back some time
after the grace period expired, they would be forced to enable 2FA
immediately.
Improve implementation to check read access to forks and add pagination.
Fixes#13648
The following optimizations where made:
- Pagination was added.
- Code to check for read permissions to forks was optimized, in the past we were doing too many queries for each project.
See merge request !2991
Removed NGProgress
In an effort to get the JS file size down, i've removed NGProgress and replaced with TurboLinks own loading indicator
Ref #13820

See merge request !3004
Changed too many changes buttons to white
Closes#13751

See merge request !3002
Small css cleanup for todos feature
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Cleanup for !2817Fixes#13816
cc @jschatz1 @skyruler @dbalexandre
See merge request !2996
Branded appearance to CE
Closes#11489
The difference with the EE version is only that there is no distinction between light and dark logos, though this wasn't used anyway. If this is fine, I'll create a MR on EE too.
TODO:
- [x] Copy docs
- [x] Make new screenshots
- [ ] Remove Custom Welcome message feature?
@rymai: I was unsure what labels to add to ping you, so I just ping you like this 😉
/cc @DouweM
See merge request !2927
Strip leading and trailing spaces in URL validator
_Originally opened at !2914 by @evuez._
It makes URLs in webhooks valid even if they contain leading and/or trailing spaces.
Spaces are hard to notice in input fields, this helps users by accepting leading and trailing spaces in webhooks URLs.
Fixes#13652
See merge request !2939
Created helper class to hide content in issue sidebar when collapsed

Closes#13764
See merge request !2968
Refactor html/css for lists and improve help UI page
* dry lists html/css removing a lot of style duplicates
* fix snippets list to match common style
* fix extra bottom margin for groups list
* improve help page ui so it looks clean
Fixes#11873
See merge request !2977