Displayed username along with nickname (when they are not identical); Requested and displayed user's avatar; Made the dialog bigger for extended names.
Added a few functions to web_backend (GetImage, GetPlain) to support getting data in multiple content-types.
Added a no_avatar icon for users without avatars.
* qt_themes: replace game_list icons
The original icons were drawn by @BreadFish64 and they do not look that good. So I got some icons in similar styles (black and white) from https://icons8.com to replace the old icons. I'm pretty sure I'm licensed to use them for Citra, by the way.
* icon licenses
In dark theme, it is very hard to see the connected/disconnected icons because they are dark too. So I added two white-coloured icons for the dark theme. This also fixed an issue where theme update does not change the icon on the status bar.
