redesign plasmoid icon Multimedia Controls & added Playbar

Add symlinks to symbolic icons for a few GNOME apps

icon JabRef PapirusDevelopmentTeam#2245

icon GNOME Connections

icon Tweet Tray (app & tray)

icon Airstrike

https://icculus.org/airstrike/

Add a few icons and symlinks for Inkscape 1.0beta2

Optimize (a bit) XCOM icons