Clarify CI/CD & AutoDevOps usage on initial setup

Problem to Solve

Saw this quote on Hacker News (https://news.ycombinator.com/item?id=18128663) in context of getting a CI/CD server setup:

Thank You! I will look into that. OTOH this is how I came to conclusion that I must go the AutoDevOps way: This is my first installation of gitlab ever. So naturally, after somehow successfully installing it on the 2nd try, everything seems to work. So - lets explore configuration options. For example we should disable registration since, well, we don't want to be a public gitlab host. After a while, after the Pages section, we come to a section named "Continuous Integration and Deployment". And there's a checkbox named "Default to Auto DevOps pipeline for all projects". And there does not seem to be any other kind of "Continuous Integration and Deployment" available so one naturally comes to a conclusion that the only way seems to be Auto DevOps. My bad.

Perhaps we can make this a bit more clear on what the difference is between CI/CD and AutoDevOps and why you might choose to use AutoDevOps or not.

cc @danielgruesso @markpundsack