Add validation errors to Merge Request form

Closes #22448

See merge request !7163

Allow admin to search for user by secondary email address

Closes #23761

See merge request !7115

New todos blank state

## What does this MR do?

Updates the blank state on todos.

### Blank state when user has previously had todos

![Screen_Shot_2016-10-12_at_12.40.35](/uploads/17d9a5a409d12bce73147e3879d9d62d/Screen_Shot_2016-10-12_at_12.40.35.png)

### Fully empty blank state

![Screen_Shot_2016-10-12_at_12.40.40](/uploads/5c0824096ced9f03b3ea5f892b70b08b/Screen_Shot_2016-10-12_at_12.40.40.png)

## What are the relevant issue numbers?

Closes #20833

See merge request !6823

Remove leftover references to coffeescript from comments and docs.

I was looking at the front-end helper spec and noticed some outdated coffeescript refs in it. So I figured it wouldn't hurt to take a few minutes and remove all the coffeescript references in CE that we don't need anymore. 

I didn't touch any coffeescript references that could potentially break anything. Just docs and code comments.

- [x] All builds are passing

See merge request !7151

It is not possible to search for a user by his secondary email address in
the Users search bar in the admin interface(/admin/users). A use-case could
 be that an admin wants to remove a specific secondary email address of an
user, because it interferes with another user. Issue #23761

This commit adds ability to search not only by main email, but also
by any secondary email in the admin interface.

The parameter is used to search users by several criretia was
called :name. This request renames it to :search_query which closer
to it actual perpose

Fix project features default values

closes #23242

See merge request !7181

Correct padding and alignment for reaction buttons

## What does this MR do?
Fixes padding and alignment for reaction buttons on issues.

## Screenshots (if relevant)

### Before
![img](https://gitlab.com/gitlab-org/gitlab-ce/uploads/ae788883aca84799fca9cd23f8e16f28/image.png)
![img](https://gitlab.com/gitlab-org/gitlab-ce/uploads/b2f5aa45dbb4899f054f839bd9046bb6/image.png)

### After
![Screen_Shot_2016-10-28_at_3.56.03_PM](/uploads/0b1affed448f6ec24fa56e7800daf753/Screen_Shot_2016-10-28_at_3.56.03_PM.png)
![Screen_Shot_2016-10-28_at_3.56.09_PM](/uploads/311bb59dc6eea8cd124232ebe647b5ef/Screen_Shot_2016-10-28_at_3.56.09_PM.png)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?


Closes #23918

See merge request !7182

Fix relative links in Markdown wiki when displayed in "Project" tab

Refers to #23806

See merge request !7218

Implement CreateProjectMembers service to make controller thin

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23566

See merge request !7170

Add a link to the Issue Boards API in main README

See merge request !7221

[ci skip]

Blacklist the OSL 3.0 license

See merge request !7171

Do not show tooltip for active element

## What does this MR do?

Change Bootstrap's default for tooltips to display them only when hovering and not for the active element.

See also here: https://getbootstrap.com/javascript/#tooltips-options

## Screenshots

### Before

![before](/uploads/c5b7bd9eba07ca61bfa5ba014d08dd1a/before.webm)

### After

![after](/uploads/d8c4a69e5a6797d8d26ab92cb96fcb2d/after.webm)

## What are the relevant issue numbers?

Closes #23794

See merge request !7105

If source branch or target branch doesn't exist in the project, display
form validation errors. Previously, this caused a 500 error code.

Fix Markdown styling inside reference links

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/18096.

Based off https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6609.

See merge request !7169

Fix project visibility level link

Fix wrong syntax for link generation.

See merge request !7201

Update tags.md

See merge request !7202

Fixes: https://gitlab.com/gitlab-org/gitlab-ce/issues/18096

Refers to #23806.

Optimize group labels page

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23684

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/1148

See merge request !7123

Closes #20833

Updated positioning of copy file path button in diffs

## What does this MR do?

Updated the positioning of the copy file path button in diffs.

## Screenshots (if relevant)

![Screen_Shot_2016-10-31_at_16.53.24](/uploads/53de39ce550855f86b90d2d9fc227f95/Screen_Shot_2016-10-31_at_16.53.24.png)

## What are the relevant issue numbers?

Closes #23591

See merge request !7203

GrapeDSL for branches endpoints

No changelog item as it doesn't change behaviour
Cherry-picket from !6330

See merge request !6630

Add ES array methods as cause of Phantom.js errors.

## What does this MR do?

Adds another example of something that causes a common error in JavaScript testing to the frontend dev docs.

See merge request !7102

Resolve "Clean up commit meta info view"

Updates commit page design   
Before:   
![Screen_Shot_2016-10-19_at_10.20.10_AM](/uploads/8737a9db01bffc019d8b2c71a943024b/Screen_Shot_2016-10-19_at_10.20.10_AM.png)
After:   
![Screen_Shot_2016-10-19_at_10.20.01_AM](/uploads/716cb902bd20dedc705a8f81f6536736/Screen_Shot_2016-10-19_at_10.20.01_AM.png)
![Screen_Shot_2016-10-19_at_10.27.01_AM](/uploads/4228575f50990a88bc828037d8fb99f2/Screen_Shot_2016-10-19_at_10.27.01_AM.png)
Closes #20892

See merge request !6994

[ci skip]
Signed-off-by: Rémy Coutable <remy@rymai.me>