Use common sharing emblem for folder-publicshare

The "user silhouette" in current folder-publicshare icon could be misleading. GNOME icon theme switched to "publish" emblem[1] (circle with 2 arrows pointing on top left and top right, frequently available on web for "share this" action). Could be good do the same in Humanity.

PS using the publish emblem in this icon could allow us to reuse "user silhouette" emblem for user-home icon. The icon representing all your personal files will have a "persona" over it. A good starting point to hide "home folder" from UI and to distinguish user-home from go-home

[1] http://git.gnome.org/browse/gnome-icon-theme/plain/gnome/32x32/places/folder-publicshare.png