Change CSS layout for logo and thumbnail section

[Esshahn]

Ideas:

• same logo concept as the App Icon
• less colorful, maybe black & white even
• probably drop the icon box, too

[Esshahn]

It could be as simple as this:

But, to be honest, I would actually do this:

• get rid of the whole black top area, which is kind of legacy from the old layout
• move the thumbnails in the grey area right on top of the big canvas
• no show a logo at all

It would be a nicer, simpler layout I think.

[Esshahn]

Changed issue title so that it reflects that we agree on changing the layout as described above makes more sense.

[nurpax]

There's some whitespace between the canvas and the screens. It might look better if the screens were sitting on top of the canvas..

But the flex layout works so that the canvas is in the middle, centered, and the screen tabs attach to the top of the window. So depending on window size, there's less or more space between these elements.

Might revisit this a bit if I want to make the canvas scalable w.r.t the app main window size.

[Esshahn]

Love it already.