Wordpress-seo: Change snippet preview tab icon when SEO and readability analysis are disabled

[andizer]

Roadmap issue: https://github.com/Yoast/roadmap/issues/101
Product owner: @jdevalk

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Problem definition

When the readability and keyword analysis are disabled I get an empty traffic light:

Proposed solution

Let's change the icon to a Yoast icon when both SEO and Readability analysis are disabled.

[jdevalk]

Let's change the icon to a Yoast icon when both SEO and Readability analysis are disabled.

[thijsdevalk]

I'd be hesitant to just change the icon, as that also kind of changes the navigation for people... I think the whole thing (including the "lights") should be greyed out.

[IreneStr]

We decided to do 3 grey bullets inside the traffic light instead of a greyed out traffic light.