Add firewall-config and firewall-applet icons

Summary:
48px color icons for firewall-config and firewall-applet. firewall-applet is a symlink to firewall-config.
22px, 16px monochrome icons for the system tray: firewall-applet, firewall-applet-error and firewall-applet-panic. firewall-applet and firewall-applet-error are symlinks to security-high and security-low, but firewall-applet-panic is a new icon because security-medium does not accurately represent panic mode.

Reviewers: VDG, Breeze, ngraham

Reviewed By: VDG, Breeze, ngraham

Subscribers: bruns, abetts, alex-l, svenmauch, kde-frameworks-devel, ngraham

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D11880