Introduce common images for repetitive documentation tasks
There are many times where we instruct the user to edit a project or visit a page that is reached via a common path. One such example is the cog wheel in the upper right corner of a project. For documentation that has an ordered list of tasks for the user to perform, we should introduce some common images and text in order to not duplicate the effort of writing docs.
For example:
1. Navigate to the main page of the project.
1. In the upper right corner, click the settings wheel.
![Image alt text](img/common/project_settings.png)
1. Etc.
The question is where should these images be placed. I was thinking something like doc/img/common/
. The caveat is that we use relative URLs, so if the document is buried under 4 or 5 levels, the markdown would look like:
![Image alt text](../../../../img/common/project_settings.png)
This is relevant to https://gitlab.com/gitlab-org/gitlab-ce/issues/17996.