Add new data to project in push, issue, merge-request and note webhooks data

_Originally opened at !2738 by @bugagazavr._

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**What does this MR do?**

Adds more data to hooks, makes repository data in all hook more dry ( use one hook_attrs method for repository data in all hooks )

**Are there points in the code the reviewer needs to double check?**

1. https://gitlab.com/bugagazavr/gitlab-ce/blob/extend-hooks/app/models/project.rb#L738
2. https://gitlab.com/bugagazavr/gitlab-ce/blob/extend-hooks/app/models/concerns/issuable.rb#L132
3. https://gitlab.com/bugagazavr/gitlab-ce/blob/extend-hooks/lib/gitlab/push_data_builder.rb#L52
4. https://gitlab.com/bugagazavr/gitlab-ce/blob/extend-hooks/lib/gitlab/note_data_builder.rb#L56

**Why was this MR needed?**

More information about user for push events, and more data about repositiry ( project )

**What are the relevant issue numbers?**

No

**Screenshots (if relevant)**

No

See merge request !2788

- Add `avatar_url`, `description`, `git_ssh_url`, `git_http_url`,
  `path_with_namespace` and `default_branch` in `project` in push, issue,
  merge-request and note webhooks data
- Deprecate the `ssh_url` in favor of `git_ssh_url` and `http_url` in
  favor of `git_http_url` in `project` for push, issue, merge-request and
  note webhooks data
- Deprecate the `repository` key in push, issue, merge-request and
  note webhooks data, use `project` instead

Also:
- Get rid of legacy :strict_mode
- Get rid of custom :email validator
- Add some shared examples to spec emails validation

This is the git default and will help to prevent false positive matches.

Closes #12706

The problem occurred because asset compilation takes a long time, so
when the asset cache didn't exist and the first test ran, it would often
(randomly) time out during the generation before the actual test even
had a chance to run.

Now we check if the cache exists before the suite runs, and if not, we
manually fire a request to the root URL in order to generate it. This
should allow subsequent tests to use the cached assets.

This allows us to implement artifacts passing: runner will download artifacts from all prior builds

Add pagination headers to already paginated API resources

Following #3045, I've added pagination headers using already available Kaminari methods.

## Pagination headers in action

![Screen_Shot_2016-01-14_at_12.14.53](/uploads/88807f754dd9aafbb24da85f6bdf9521/Screen_Shot_2016-01-14_at_12.14.53.png)

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I've also added a shared example to test paginated API resources.

A possible next step would be to paginate all the API resources that return an array.

See merge request !2426