Improved design of Global Settings

[marmarta]

Transitional form: the functionality is the same, changes are
mostly visual, with only a minor addition of Version no,
release info link and version link.

fixes QubesOS/qubes-issues#6858

[marmarek]

Font sizes here are huge, it barely fits on the screen (and I got a scrollbar). Can you use the same font size as in the manager? I've just checked - it does use whatever you set in global appearance settings, so probably it will be enough to simply not override it with any explicit value.

And also - I don't like the new buttons at the bottom, because:

• they are in different place than in every other dialog
• they have only text and no graphical (or color) indicator of the action - again contrary to every other dialog in the system

[marmarta]

@marmarek , I pushed a better, improved version. Could you check if it's still super big on a system that's not custom-dpi-ed to hell?

[marmarta]

@marmarek , could you check if this looks better on your end? Looks good on mine but as we established, well, this means little.