* Remove experimental pinning feature again and instead allow using a
normal window
* Pinning made it inconvenient to close the (frameless) window again
* Pinning required hiding/showing the window which didn't look very
nice (and setting flags directly via `QWindow` didn't work as well)
* As normal application/window positioning issues on Wayland are less
problematic (and those aren't going to be fixed any time soon, if at all)
* Allow using icons from freedesktop.org icon theme for most ForkAwesome
icons if available
* Let's not use it for the nested list of details in the models for now
* See https://github.com/Martchus/syncthingtray/issues/121