Blur apps that are behind the apps menu

[Ewertonios]

Problem

Sometimes it's kind of distracting to use the applications menu when the desktop is full of apps because I can't distinguish it well from the others apps.

Proposal

I would like the apps behind it could be blurred, faded, dimmed, or anything else that would allow for better focus on the appmenu. The same could be done for the other wing panel components.

Other solution could be a full screen mode for applications menu #574.

Prior Art (Optional)

[teamcons]

"slightly dim" everything else would be somewhat more "in line" with Elementary's design, i feel. Could be an idea for inactive windows as a whole.