[documentation] Make gitlab guides more prominent

Think about where the gitlab tutorials should be. They are a bit hidden at the bottom of tools now. Perhaps "git and gitlab" should be their own section so they are really easy to find when people are on-boarding. Could also nest all the pages under "tutorials" then... :)

To Do:

• Move gitlab etc tutorials to its own section (alongside tools)
• Add a gitlab sticker on how page
• Think about whether stuff like "what to include in your repo" should be in the gitlab section rather than analysis. All gitlab mentions in other section should then link back to the main gitlab area.