new icon for panel profiles

[philipzae]

In order to distinguish between panel preferences and panel profiles, a new icon for panel profiles should be created.

A package icon is used in the panel preferences dialog to launch panel profiles, so an icon similar to that should be created.

It would mix the package icon with the xfce-panel icon, possibly like this.

[m4u9]

The icon comes from xfce upstream and we are already in the process to revamp all xfce stock icons targeting 4.16 release. thanks for the suggestion though :)