Secrets yml for GitLab CI

Fixes #664

See merge request !409

Check if SElinux is enforced and skip loading module if disabled.

No one supplied MR to solve it so this fixes #501 and confirmed on #660

See merge request !408

Add builds directory configuration for GitLab CI.

Fixes #659

See merge request !407

Set net.core.somaxconn kernel parameter for unicorn

Set net.core.somaxconn kernel parameter to a value equal or higher then unicorn backlog_socket. The default kernel value is 128 which is lower then the default unicorn backlog.

Closes #656

See merge request !405

Add docs about using custom certificate. Fixes #626

See merge request !406

Posttrans for rhel

Different way of handling #649 .

Also fixes #528

See merge request !402

Dont start if path is nonexistent

This should handle #272 .

Even when /opt is mounted as a separate filesystem, systemd will attempt starting GitLab and if for some reason all filesystems are not mounted this will make GitLab start fail.

Fix contains a move of the service file to [the installed packages unit location](http://www.freedesktop.org/software/systemd/man/systemd.unit.html) of `/usr/lib/systemd/system` and also adds a condition to start GitLab only after all system services are loaded.

See merge request !403

No need to symlink gitlab services, remove old symlink. With systemd wait for system services to fully start before starting gitlab.

Use Omnibus new syntax for building projects.

See merge request !404