Switch from tabs for pressed applets to tasks.
- Tabs should be avoided because it's quite semantically incorrect and I need to change tab style in another patch to make them look prettier but that would break clicked plasmoids
- Tasks appearance is consistent with the system tray that's next to it; plus, I think that it looks prettier than just a line.
Alternatively, a hover view-item effect could be used, especially since the panel margin could be higher in third party themes.