core: Implement global anti-link functionality
core: Implement global anti-link functionality

You can use this functionality to block a person to get linked
with any other person.

https://bugzilla.gnome.org/show_bug.cgi?id=724058

pwithnall/folks,pwithnall/folks,pwithnall/folks,GNOME/folks,GNOME/folks,GNOME/folks