Added dropdown to list all projects on project header

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/4212

When clicking the current project name, it shows a dropdown menu with a list of all projects for that group or user.

When closed:

![Screen_Shot_2016-01-14_at_19.17.44](/uploads/a7258ba388dba238fc2f0468711fc729/Screen_Shot_2016-01-14_at_19.17.44.png)

When open:

![Screen_Shot_2016-01-14_at_19.17.51](/uploads/716533d9eb44b123c5fdff36a4740489/Screen_Shot_2016-01-14_at_19.17.51.png)


cc. @jschatz1

See merge request !2438

[ci skip]

Consistent rails_socket use.

[ci skip]

See merge request !2596

Send raw Git blobs via gitlab-workhorse



See merge request !2451

explicitly call script with bash for consistency

simpler than telling users to set script executable

[ci skip]

See merge request !2621

Bump New Relic gem version to avoid warnings in Web page

This version has support for Grape, so we should consider removing
the newrelic-grape gem as well:

https://docs.newrelic.com/docs/agents/ruby-agent/frameworks/grape-instrumentation

See merge request !2578

Fix add_pagination_headers to keep request parameters in Link header

Originally opened at !2321. Closes #5904. /cc @Michi302

See merge request !2674

Updated contributing guide for stable releases

[ci skip]

See merge request !2638

Lazy Git blobs

To prevent madness like loading a 100MB file into Ruby's memory just
to decide whether it is binary or text.

See merge request !2663

Allow "@" in file names and path

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/4111

See merge request !2665

Generate valid (RFC 2111) Message-ID in email rejection mailer

Use a Message-ID that is RFC 2111 compliant. This fix is consistent with
how the Message-ID is generated in the 'notify' mailer.

See merge request !2656

Fix typo indentation in CI projects' API



See merge request !2561

Add notes about the regression issues to CONTRIBUTING.md

[ci skip]

See merge request !2661

Expand Git instrumentation

This instruments some extra `Gitlab::Git` code as well as a collection of `Rugged` constants.

See merge request !2664

Fixes #12784