This reverts merge request
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21946

Also:

- Replace DevOps image with one with all stages.
- Further restructure page.
- Edit and tabulate lower part of page.

Includes:

- New enhanced overview button.
- Aligning the top table.
- Start of thorough edit and table reorganisation.

- Adding icons.
- Adding more stages.
- Alphabetising tables.
- Adding more links.
- Andother minor improvements.

Includes:

- Orientating page around audiences.
- Adding descriptions to all links.
- Light restructuring.
- Minor fixes.

The link to "GitLab Cycle Analytics" pointed to
/user/project/cycle_analytics.md and not /help/user/project/cycle_analytics.md.
This is caused by an issue with the markdown renderer. This temporary fix
corrects the link by inserting a line break.

Previous one returned HTTP 404. It was discussed in http://gitlab.com/gitlab-com/marketing/general/issues/1966
that it is preffered to use /press based git cheat sheet pdf because it
is opened in browser's pdf viewer by default rather than downloaded.