Mixing ForkAwesome icons too much with the regular icon theme doesn't look
good (depending on the theme) so let's prefer ForkAwesome icons within the
tray widget which already uses ForkAwesome in some places like certain
buttons and models. This makes it also look more in-line with Syncthing's
web UI. For context menus and dialogs let's prefer system icons because
there are hardly any ForkAwesome icons used/required so far and it is maybe
nicer to be in-line with the system here.
Martchus