Fix setting window size oddities

[MortimerGoro]

Fixes #990

[bluemarvin]

I still think we need to rethink the display and max display settings.

[philip-lamb]

This fixes the incorrect size when a width of 800 is set, but not that changing the width still doesn't fix the actual size of the web content pane; it only changes the height (so that the aspect ratio is correct).

[bluemarvin]

I think there is some confusion over what the window size field represent. This is actually the default window size. So when the user clicks the 1x button on the resize button bar, this is the size the window should return to.

[MortimerGoro]

I agree that it's confusing. I understand it as the window pixel size for 1x world size: similar to a zooming feature, show more or less pixels in the same world meters size.

Should we just remove these settings? What's the use case to have them?

[bluemarvin]

I think it should at least be renamed. I don't see anything wrong with allowing users to set the default size of a window.

[philip-lamb]

OK, let's get this change in first and we can consider labelling change separately.