Make popups fill the entire window

[JaiganeshKumaran]

Today popups opened inside the window don't cover the full window. While you could click anywhere else, I find it confusing and hard to use. Consider making it full the entire window instead.

[BreeceW]

I’m thinking about making the settings a page following standard navigation patterns. Photo viewer could be more of an overlay of the whole window (see GroupMe UWP for example).